Technical Medicine, the first hundred graduates by University of Twente

TECHNICAL MEDICINE THE FIRST HUNDRED GRADUATES

CONTENT Preface............................................................................................... 3 Track Medical Signaling..................................................................... 5 Track Robotics & Imaging................................................................ 39 Track Reconstructive Medicine........................................................ 83 Overview of the first hundred graduates sorted per track............... 111 2

PREFACE

In 2003 a new bachelor’s programme ‘Technical Medicine’ was introduced aiming to fill the gap between technology and medicine in health care. With the start of the master’s programme in 2006, the graduation of the first student in 2009, the first PhD graduate in 2011 and MIRA that has become one of the leading institutes in research in Biomedical Technology and Technical Medicine, a new discipline in health care is born: the discipline of Technical Medicine. Technology is of increasing importance in health care. Medical technology is generally defined as “the techniques, drugs, equipment, and procedures used by health care professionals in delivering medical care to individuals, and the systems within which such care is delivered”. To ensure responsible and safe innovative use of technology in medical care a solid scientific, medical, and engineering background is required. Such a background is realized in a new discipline which integrates the medical and technical domain into a new expert domain. This new discipline provides the academic training for a new health care professional: the technical physician. The technical physician is a true scientist-practitioner, who has the medical knowledge and skills, professional behavior, and problem-solving approach to design improved, safe technological diagnostic strategies and therapies for specific patient problems and has the (legal) competence to apply these in direct patient care. It is with tremendous pride and pleasure that we present to you the abstracts of the first 100 master theses of Technical Medicine. We hope these abstracts will provide the reader a more in depth insight in the field of expertise and competences of the technical physician. And that it will make the reader as convinced as we are of the added value of this new professional in health care.

Heleen Miedema, programme director Technical Medicine

TECHNICAL MEDICINE ROTATION PROJECTS

TRACK MEDICAL SIGNALING

ELECTROPHYSIOLOGICAL MEASUREMENTS ON SENSORIMOTOR INTEGRATION Inge Brons

This study was aimed to take a first step in the evaluation of a measurement protocol that combines motor and somatosensory evoked potentials (MEP and SEP respectively) and corticomuscular coherence (CMC) in different conditions in order to investigate sensorimotor system functioning. Healthy controls were compared with three patient groups, in order to determine whether the measurement method was able to discriminate well between the extremes of the spectrum of pathologies that affect sensorimotor functioning. The patient groups consisted of patients with neuropathy, torticollis spasmodica and multiple sclerosis, representing respectively disorders in the sensory system, sensorimotor integration and motor system. Besides, healthy controls of two different age groups were enrolled in order to determine to what extent age must be considered in the interpretation of the results.

The protocol was executed in twelve younger and thirteen older healthy subjects, three patients with neuropathy and five with torticollis spasmodica. Sensory influence on motor control was expressed in the majority of subjects by reduced MEP amplitudes as well as a reduction in corticomuscular coherence due to sensory stimulation. Reversely, the effect of motor activity on the processing of sensory information was observed as a reduction of SEP component amplitudes during isometric contraction. Some deviant MEP and CMC results were found for the torticollis group, that could be related to their abnormalities in sensorimotor integration. Furthermore, the SEP and CMC appeared to be susceptible to age. The lack of a multiple sclerosis patient group as well as the small sample sizes for both other patient groups implied that no definite conclusions could be drawn about the hypothesis that the protocol would be able to discriminate well between these groups. It is advised to continue the evaluation of the protocol with consideration of the recommendations that result from the current study.

University Medical Center Groningen, Clinical Neurophysiology - N.M. Maurits (UT: T. Heida, B. ten Haken)

FUNCTIONAL AND PHYSIOLOGICAL OUTCOME MEASURES FOR rTMS IN HEALTHY SUBJECTS Susan van Maarseveen In many fields in medicine, possible therapeutic applications of rTMS are expected. Some examples are the treatment of depression, tinnitus, movement disorders and rehabilitation. However, the influence of all parameters of a stimulation protocol, the right choice of out-come measures and biological factors influencing the results are all factors that are not fully understood. The objective of this study was to assess the relation between a number of physiological and motor-related functional outcome measures, in a single-blinded, randomized, standardized, placebo-controlled cross-over setting. Ten healthy subjects participated in the study. Each subject underwent two sessions of rTMS stimulation and one session of placebo stimulation, with before and after each stimulation session measurement of 8 outcome measures. Functional outcome measures were the maximal hand grip force, maximal finger tapping frequency, maximal diadochokinesis frequency and a circle tracing task. Physiological outcome measures were the motor evoked potential recruitment curve, intracortical facilitation, intracortical inhibition and the contralateral silent period duration. In both the functional and the physiological outcome measures no relevant effects of the rTMS were found. In the physiological outcome measures, this can be caused by errors in the coil positioning, which can be avoided in future studies by the use of coil neuronavigation. The repeatability of the functional outcome measures was good. The attention of the subjects may have large influence on the physiological responses and should be controlled in further studies. The effect of the thetaburst stimulation is not proven. With the protocol designed in this study, with the adjustments provided, relations between the functional and physiological outcome measures can be expected to be found in healthy subjects. These relations can help to improve the choice of outcome measures in therapeutic studies.

University Medical Center Groningen, Clinical Neurophysiology - N.M. Maurits (UT: M.J.A.M. van Putten, A.de Keijzer)

PREDICTING SUCCESS OF VAGUS NERVE STIMULATION FROM INTERICTAL EEG Leonie Melching

PURPOSE Vagus nerve stimulation (VNS) has been shown to be an effective treatment for drug resistant epilepsy in numerous patients. However, it is still not possible to predict which patients will profit from VNS. In this pilot study, we identify predictive interictal EEG features for the success of VNS treatment.

METHODS 19 Patients with medically refractory epilepsy and an implanted VNS system were included. Interictal EEG registrations, recorded before implantation, were retrospectively analyzed. EEG features analyzed were the brain symmetry index (BSI), absolute and relative power and mean frequency for four frequency bands. Prediction models with individual and combinations of EEG features were made. Reduction of 0% and 50% seizure frequency was used to define the responders.

Difference between BSI for responders and non-responders to VNS measured before the start of treatment. (Definition responders: Left: > 0% seizure reduction; Right: > 50% seizure reduction) * p < 0.1 ** p < 0.05

RESULTS 9 Out of 19 patients reduced seizure frequency for at least 0% and 7 patients had at least 50% seizure reduction. Overall, we find higher BSI for non-responders compared with responders. BSI of the delta, theta and alpha band could significantly discriminate between responders and non-responders. BSI of the delta frequency could predict any seizure reduction with a sensitivity and specificity of 70% and 77.8%, respectively. A combination of BSI of the alpha band and mean beta frequency could significantly predict seizure reduction of more than 50% with a sensitivity of 85.7% and a specificity of 91.7%.

CONCLUSION Symmetry values show promising results in predicting the success of VNS. These pilot results encourage further studies enrolling larger number of patients and may contribute to improved treatment and understanding of the working mechanisms of VNS on seizures.

Medisch Spectrum Twente (Enschede), Clinical Neurophysiology - M.J.A.M. van Putten, C.C. de Vos (UT: T. Heida)

MONITORING THE BRAIN IN THE ADULT ICU Marleen Cloostermans

PURPOSE

CONCLUSION

The EEG is well-suited for continuous brain monitoring in neurologic patients in the ICU, as the EEG is very sensitive for potential risks as ischemia and (non-convulsive) seizures. However, for a real-time interpretation of the EEG, quantitative EEG (qEEG) features and an adequate presentation are required. We have implemented and evaluated a system for real-time detection of epileptiform discharges and ischemia.

An EEG classification system is presented for monitoring purposes at the ICU. The proposed system satisfies the requirement that the monitoring system is able to interpret most common EEG patterns that are observed in neurologic patients at the ICU: normal EEGs, iso-electric EEGs, low voltage EEGs, burst suppression patterns, hypofunctional EEGs (with regional or diffuse slowing), EEGs with GPDs and EEGs with seizure activity. At present, an initial evaluation of the system is performed in our ICU.

METHOD Several qEEG features, for example the nearest neighbour coherence and autocorrelation analysis are implemented and combined into a single overall classifier. This classifier consists of a decision tree, which is constructed based on prior physiological and pathophysiological knowledge and is improved after the use of two training sets. An independent test set was used for evaluation of the classifying system. In total 61 EEG 5 minute epochs were used.

RESULTS The results show that 53 out of the 61 EEGs (87%) are classified correctly. These results can even be improved after adaption of more data sets in future research. A new representation of the output of the decision tree is proposed here. It has been demonstrated that the system is suitable for real-time monitoring.

Example of the monitor of a patients with a generalized nonconvulsive status epilepticus.

Medisch Spectrum Twente (Enschede), Clinical Neurophysiology - M.J.A.M. van Putten, C.C. de Vos (UT: T.Heida, A. de Keijzer)

CRITICAL ILLNESS POLYNEUROMYOPATHY Electrical stimulation as possible therapy Esther ter Braack

INTRODUCTION

RESULTS

Muscle weakness in patients admitted to the Intensive Care Unit lengthens duration of weaning, mechanical ventilation and hospital stay. One of the causes of muscle weakness is critical illness polyneuromyopathy (CIPM). The incidence of CIPM is about 50% in patients who receive prolonged mechanical ventilation, have sepsis or multiple organ failure. Despite many previous studies, the pathophysiology and risk factors of CIPM remain unclear. More importantly, there is yet no therapy for this disease. Electrical stimulation has been shown to improve muscle strength and prevent muscle atrophy in many different patient categories. After a literature review, a pilot study was set up in our thoracic Intensive Care Unit (ICU). We wanted to evaluate the effect of electrical nerve stimulation on muscle strength in patients with CIPM. Our second goal was to obtain more information on the incidence, severity and course of CIPM in patients after cardiothoracic surgery.

A limited number of 3 patients were included and only in 1 patient the protocol was completed. In this patient, muscle force in the stimulated leg increased by 10%, while in the non-stimulated leg muscle force decreased by 10%. EPS results in this patient showed some indications of CIPM, but a definite diagnosis could not be made.

CONCLUSION Because of the small number of included patients, no conclusions can be drawn about the effect of electrical nerve stimulation on muscle force or EPS results. However, we did show that electrical stimulation is feasible and safe in ICU patients. The results from 1 patient suggest that a beneficial effect of electrical stimulation on muscle force may be possible.

METHODS Patients with an expected ICU stay of > 2 days were included for 10 days in this prospective study. Electrophysiological studies (EPS) were performed daily and muscle strength of the tibialis anterior (TA) muscle in both legs was measured with a handheld dynamometer when the patient was awake and cooperative. Electrical nerve stimulation was applied during 9 days on the TA and extensor brevis muscle in one leg. The study was approved by the medical ethics committee. Placement of the electrodes (black dots) on the lower leg.

Medisch Spectrum Twente (Enschede), Thorax ICU & Clinical Neurophysiology - J. G. Grandjean, J.W. Vermeijden (UT: M.J.A.M. van Putten, B. ten Haken)

SIGNAL ANALYSIS OF INITIAL VENTRICULAR FIBRILLATION WAVEFORM PATTERNS IN INTRACARDIAL ELECTROGRAM RECORDINGS FOR PREDICTING SHOCK SUCCESS Veronique Meijborg Ventricular fibrillation (VF) is a life-threatening cardiac arrhythmia and appeared to be the initiating factor in the majority of the out-of-hospital cardiac arrests (OHCA), often resulting in sudden cardiac death. In the past, many research is performed to elucidate the electrophysiological mechanism of VF enabling us to develop new therapies. For this reason investigators tried to identify in recent years a number of signal characteristics of VF waveform pattern. Unfortunately still less is known about the initial pattern or onset of the VF waveform. Therefore the objectives were the characterization of the initial waveform pattern of VF and the evaluation of the predictability of the defibrillation success. Electrograms (EGMs) of ventricular fibrillation right after onset, extracted from data of implantable cardioverter defibrillators (ICDs), were collected and subsequently analyzed with a mathematical program using the Fourieranalysis. From the resulting power spectral density a number of signal characteristics, related to the frequency and regularity of the signal, were determined. As a result we

characterized the waveform pattern of the initial VF by a mean fundamental frequency of 5.07 Hz. This frequency usually coincided with the dominant frequency, implicating that it is the most abundant frequency in the signal. The waveform pattern is additionally characterized as rather â&#x20AC;&#x2DC;peakyâ&#x20AC;&#x2122; and complex, due to the presence of higher harmonic frequency peaks. The results appeared to be comparable to the literature. Besides we demonstrated that the extent of regularity is strongly positively related to the bandwidth of the fundamental frequency, and is negatively related to the median frequency, proportion of powers of the first harmonic to fundamental frequency and the number of frequency peaks. We concluded subsequently that within the initial VF waveform pattern (yet) no differences in the signal characteristics were detectable in VF preceding a successful versus an unsuccessful first shock, making it useless to evaluate the predictability of the defibrillation success.

Radboud University Nijmegen Medical Centre, Cardiology - J.L.R.M. Smeets (UT: P.H. Veltink, A. de Keijzer)

OPTIMIZING THE DELINEATION OF FOCAL EPILEPSY Refinement of MEG source imaging and the ictal onset detection in ECoG Karin van de Groep Patients suffering from focal epilepsy syndromes are not always adequately controlled with anticonvulsive drugs. Epilepsy surgery might then be a good option when the epilepsy starts at a well-defined area in the brain. The gold standard for delineating this area is chronic intracranial EEG, where electrodes are placed either directly into the brain (depth-EEG) or over the surface of the brain (electrocorticography, ECoG).

Comparison between these source imaging methods and the ECoG showed that not just one MEG method is the best. Each method has its advantages and disadvantages. In all methods the clinician has to be careful in the interpretation of the results.

MEG might also be useful in detection of the seizure onset zone (area of the cortex from which clinical seizures are generated). Occasionally a patient gets a seizure during MEG registration. Seizure onset is not as well-defined as is interictal activity. In SAM(g2), visual interpretation is avoided. The seizure onset zone found by analysis of the ictal data with SAM(g2) was compared to the seizure onset zone found by using the ECoG. Seizure onset detection in the ECoG was improved by applying SAM(g2) to the data.

Chronic intracranial EEG is however invasive and only part of the brain can be covered with electrodes. It has been suggested that interictal MEG may be a substitute to ECoG or at least can help to plan electrode placements. With MEG, interictal data can be recorded which helps to delineate the irritative zone (the area of cortical tissue that generates interictal spikes) and thereby the epileptogenic zone (cortex that can generate epileptic seizure).

Result of MEG source imaging method SAM(g2).

I n the final part of the research an algorithm was devised to define seizure onset in the ECoG. The algorithm found out to be a useful tool in detecting the ictal onset zone in patients with gamma and/or beta onset. Using the three approaches examined in this study, delineation of focal epilepsy is improved: this study has refined MEG source imaging, which makes electrode planning in the pre-surgical evaluation in focal epilepsy more reliable, and the delineation of the ictal onset zone less subjective.

Result of MEG source imaging method sLORETA Several source localization methods have been described in literature, but it is not known which method can be used best. Three source localization methods, multiple signal classification (MUSIC), standardized low-resolution electromagnetic brain tomography (sLORETA) and Synthetic Aperture Magnetometry kurtosis (SAM(g2)) were compared to the gold standard of ECoG. An advice was given to clinicians which strategy using MEG data provides the most reliable localization and delineation of the irritative zone of patients with focal epilepsy.

Intracranial EEG (ECoG).

University Medical Center Utrecht, Clinical Neurophysiology - F.S.S. Leijten, G. Huiskamp (UT: M.J.A.M. van Putten, A. de Keijzer)

qEEG MEASUREMENTS DURING 足CEREBRAL GAS EMBOLISM AND THE 足EFFECTS OF HYPERBARIC OXYGEN Xavier Vrijdag INTRODUCTION

RESULTS

Cerebral arterial gas embolism (CAGE) is the occlusion of the cerebral blood vessels caused by diving accidents (lung rupture) and various clinical situations. We use air injected into the cerebral vasculature of the pig as an animal model for CAGE. The effect on brain function was previously measured in this model using intracranial pressure (ICP), microdialysis and brain oxygenation. We hypothesized that quantitative EEG (qEEG) would provide additional physiological information as it is very sensitive for changes in neuronal function due to hypoxia and ischemia.

After injection of 0.05 ml/kg or 0.1 ml/kg air the ICP increased, but for the animals that received 0.025 ml/kg air the ICP did not rise. In the 0.1 ml/kg group the ICP increased to values that correspond with brain herniation (cerebral perfusion pressure < 30 mmHg). The tBSI showed a nonsignificant difference between the three groups: tBSI did not increase after injection of the lowest amount of air, while both higher groups showed increasing tBSI values. In the 0.025 and 0.05 groups the mean amplitude remained above 5 uV. In the 0.1 group it decreased to 5 uV within one hour and deteriorated to iso-electricity in the next hour. The ADR, SEF and sBSI did not show a difference between the groups. The tBSI and mean amplitude showed a differentiation between the hyperbaric treatment and control group, however this was not significant.

MATERIAL & METHODS In fifteen anesthetized pigs (35-40 kg) air (0.025, 0.05 or 0.1 ml/kg) was injected into the ascending pharyngeal artery in order to induce CAGE. The ICP, microdialysis parameters and brain oxygenation were measured using intraparenchymal probes. Off-line EEG analysis was used to determine the effects on neuronal function during the two hours following embolism. As a measure for global EEG changes, we applied the alpha-delta ratio (ADR), spectral edge frequency (SEF), spatial brain symmetry index (sBSI) and temporal brain symmetry index (tBSI). The mean amplitude of the EEG signal was used to determine iso-electricity (amplitude < 5 uV). In nine experiments (0.05 ml/kg) the measuring time was extended to nine hours after embolism, of which four were treated after four hours with hyperbaric oxygen using the US Navy treatment table 6.

DISCUSSION & CONCLUSIONS EEG differences between the groups of animals were extensive and qEEG can objectively assess and quantify these differences in neuronal function. The tBSI is a sensitive feature to track changes in neuronal function due to CAGE, while the mean amplitude objectively determines isoelectricity. Due to the physiological nature of the EEG measurement, evaluating synaptic function, qEEG was able to show changes in neuronal dysfunction at an earlier time point than ICP, since increased pressure due to brain oedema is a relative late sign in the cascade of neuronal damage. This study shows that qEEG monitoring is a useful tool to improve the CAGE model. The effect of hyperbaric treatment might be of benefit on neuronal function, visible in the tBSI and mean amplitude. In the current research we observed a large range of effects visible after equal amounts of air. By using the qEEG to define the right dose, a more standardized effect might be obtained.

Academic Medical Center (Amsterdam), Hyperbaric Medicine - R.A. van Hulst (UT: M.J.A.M. van Putten, A. de Keijzer)

AMBULATORY MONITORING OF GAIT DISORDER IN PARKINSONâ&#x20AC;&#x2122;S DISEASE Sarvi Sharifi

Postural instability and gait disorder (PIGD) is a disabling feature of idiopathic Parkinsons disease (PD) and difficult to adequately estimate in clinical practice. The objective of this study was to design a quantified yet practical system which is able to detect and classify Quality of Waling (QoW) in patients with Parkinsons disease, using sensors that are suitable for ambulant monitoring (accelerometer+gyroscope). Furthermore, we investigated if the number of sensors used in this ambulatory system could be reduced from three to two sensors without losing information. For this study, sixteen patients with a confirmed diagnosis of idiopatic Parkinsons disease (HY I-IV) and eight healthy age-matched controls were included. Movements of the lower limbs and lower trunk were recorded using three accelerometers/ gyroscopes attached to the lower trunk, thigh and foot. The subjects were required to walk along a rectangular trajectory, and a predefined trajectory designed to reflect home environment and elicit freezing of gait in PD (the socalled FOG trajectory). Furthermore, symptom severity was established with standard clinical test (Unified Parkinsons disease rating scale, Timed-up-and-go test, 10 meter walking test, Freezing of Gait questionnaire, Falls efficacy scale). First, the actual motor activity of the subject was classified to distinguish between gait and static events. This is done by using an activity classifier described previously in literature using a trunk, thigh and foot sensor. By developing a new peak detection algorithm sensitive enough to detect steps using data from the trunk sensor, it was concluded that a modified activity classifier, using two sensors (trunk and thigh) instead of three was sufficient to discriminate between lying, sitting, standing and walking. This modified activity classifier showed a 95.6% accuracy compared to the original activity classifier.

Furthermore, we tested the validity of the reliable QoW features by comparing them between groups (controls versus PD in several stages of the disease) and by comparing the quantified QoW features with clinical scores of symptom severity. Variability computed from the trunk or foot was able to distinguish between PD and control (p<0.01) even in the FOG trajectory. Symmetry could only be obtained from the trunk sensor and gave significantly differences between PD and control. The variability feature from the trunk and foot showed the same significant correlations with the clinical scores. The episodic QoW features included in this study were the transition time of sitting to standing and freezing of gait. The transition time correlated well with the relevant UPDRS item (rising from a chair r=0.55), requiring a trunk and thigh sensor. Freezing of gait was classified by investigating shuffling (freezing index) and hesitation (time from sitting to walking). From the results obtained, the foot sensor was required for detecting episodic QoW features accurately. In conclusion, first we were able to accurately differentiate various motor activities (i.e. sitting, standing or walking) using only a trunk and thigh sensor instead of a trunk, thigh and foot sensor. Second, ambulatory assessment using accelerometers proved a reliable and valid method to assess quality of walking in PD patients. Compared with the foot sensor, the trunk sensor yielded more information as continuous QoW features (e.g. step variability and symmetry) were concerned. The foot sensor seemed better than the trunk sensor in detecting episodic QoW features (i.e. freezing of gait), however the actual number of freezing episodes encountered during this study was too low to draw definite conclusion on this topic.

Second, after periods with walking had been adequately identified, new algorithms were developed that assessed the Quality of Walking (QoW). These algorithms were applied to data from both the trunk and the foot sensor, and we compared which of these two sensors gave the most reliable and valid results. The QoW features tested were divided in continuous and episodic features. The continuous QoW features were step/stride duration, stride length, walking speed, duration variability and symmetry. Test-retest reliability of the variability features computed from the trunk as well as the foot found good correlations (ICC > 0.8). 14

Medisch Spectrum Twente (Enschede), Clinical Neurophysiology - J.P.P. van Vugt (UT: T.Heida, D.G.M. Zwartjes, M.J.A.M. van Putten)

EFFECTS OF LEVOSIMENDAN ON DIAPHRAGM FUNCTION IN HEALTHY SUBJECTS Jonne Doorduin RATIONALE

MAIN RESULTS

The capacity of the diaphragm to generate pressure is reduced in patients failing to wean from mechanical ventilation. However, there are no specific interventions available to improve strength or counteract fatigue of the diaphragm in critically ill patients. Recently, it was shown that levosimendan enhances the force generating capacity of diaphragm fibers in vitro by increasing calcium sensitivity of force generation without increasing energy demand. The objective of this study was to investigate the effects of the calcium sensitizer levosimendan on in vivo human diaphragm function.

The placebo group showed a 9% (P =0.01) loss of Pdi,tw after loaded breathing, whereas no loss in contractility was observed in the levosimendan group. Neuromechanical efficiency of the diaphragm during loading improved by 21% (P < 0.05) in the levosimendan group. Baseline center frequency of the EMGdi was reduced after levosimendan administration (P < 0.05). Administration of levosimendan did not increase Pdi,max.

METHODS In a randomized double-blind placebo-controlled design, 30 healthy subjects were treated with levosimendan or placebo. An initial bolus of 40 μg/kg was administrated, followed by continuous infusion of 0.1/0.2 μg/min/kg. Subjects performed 10 min loading tasks before and after study drug administration. Transdiaphragmatic pressures (Pdi) and diaphragm electromyography (EMGdi) were measured using a multi-electrode esophageal catheter with pressure balloons. Neuromechanical efficiency of the diaphragm, expressed as the ratio of Pdi to EMGdi amplitude and center frequency of the EMGdi were measured during loaded breathing. Cervical magnetic stimulation of the phrenic nerves was performed to elicit twitch Pdi (Pdi,tw). In addition, maximal voluntary inspiration against an occluded valve was performed to asses Pdi,max.

CONCLUSIONS The calcium sensitizer levosimendan improves neuromechanical efficiency and contractile function of the human diaphragm. These findings suggest a new therapeutic approach to improve respiratory muscle function in patients with respiratory failure.

Esophegeal pressure (Pes), gastric pressure (Pes) and electromyography of the diaphragm (EMGdi) are obtained simultaneously via the esophageal catheter and visual feedback is presented to subject. Cervical magnetic stimulation of the phrenic nerves is performed using a magnetic stimulator with a circular 90 mm coil. DAQ = Data acquisition device.

Radboud University Nijmegen Medical Centre, ICU & Clinical Neurophysiology - L.M.A. Heunks, D.F. Stegeman (UT: M.J.A.M. van Putten, B. ten Haken)

QUANTIFICATION OF MYOTONIA IN NON-DYSTROPHIC MYOTONIC SYNDROMES Willemijn van der Kooi BACKGROUND

RESULTS

Non-dystrophic myotonic syndromes (NDMs) can be separated in chloride (ClCh) and sodium channelopathies (NaCh). They share the feature of myotonia: a prolongation of skeletal muscle relaxation time (RT) following contraction. Sustained exercise leads to decreased myotonia also called warm-up phenomenon, except for paramyotonia in which it leads to increased myotonia. Due to the start of a drug trial for myotonia in patients with NDMs, a quantitative outcome measure for myotonia is needed. There is currently no method for quantifying myotonia in NDMs. In this study we want to investigate whether handgrip myometry and muscle elastography measurements can be used to determine quantitative and reproducible outcome measure for myotonia.

Prolonged RT and warm-up were most prominent in the 505% part of the force curve and during the first handgrip. The RT 50-5 of the first handgrip was significantly prolonged in patients when compared to controls and day-to-day reproducible (ICCs: 0.78-0.95). A significant difference in warmup was found between controls and patients. Analysis of Dicom images did not results in strain estimations that could be used for determination of RT. It only resulted in displacement curves, which resembled in axial direction the force curve, but not in lateral direction.

METHODS Five healthy controls, five genetically confirmed NaCh patients and five genetically confirmed ClCh patients participated in ultrasound measurements to acquire Dicom images and in force recordings, which were simultaneously conducted during 6 trials spread over 2 days. A trial consisted of 6 maximal handgrips. Outcome measures per handgrip were RT from 90 to 5% (RT 90-5), 90 to 50% (RT 90-50) and 50 to 5% (RT 50-5) of the force curve. Warm-up phenomenon was estimated from the difference in RT between first and sixth handgrip. Dicom images were analyzed to determine muscle displacement and muscle strain using cross-correlation between images. Muscle displacement curves were compared with muscle force curves.

CONCLUSION For patients with NDMs, the RT 50-5 of the first handgrip measured by handgrip myometry is a day-to-day reproducible outcome measure for myotonia. Muscle elastographic measurements could not be used for determination of an outcome measure for myotonia.

Shown is the experimental set-up for combined measurement of handgrip and muscle elastography. The arm lies in the fore-arm support while the hand grips the force recorder and the US probe is placed on the fore arm. EMG electrodes are covered with paper towels to prevent leaking of ultrasound gel on to the electrode surface. 16

Radboud University Nijmegen Medical Centre, Neurology & Clinical Neurophysiology - G. Drost, D.F. Stegeman (UT: M.J.A.M. van Putten, A. de Keijzer)

ALTERNATIVE METHOD FOR NON-INVASIVE POSITIVE AIRWAY PRESSURE THERAPY IN OSAS PATIENTS Lisette Rohling INTRODUCTION Obstructive sleep apnea syndrome (OSAS) is the most common sleep disorder, causing excessive daytime sleepiness. The mainstay of medical treatment of OSAS is administration of non-invasive positive airway pressure (PAP) therapy during sleep. Two kinds of PAP devices are available, the continuous PAP (CPAP) device which applies a fixed level of pressurized air, and the auto-adjusted PAP (APAP) device which adjusts the magnitude of the pressure to the optimal level in response to varying conditions over the night. APAP has generally been accepted as an alternative to CPAP in the treatment of OSAS. Meta-analysis has shown that APAP can control OSAS as effectively as CPAP, with the use of lower mean pressures. Although, this advantage is often outbalanced by higher peak pressures which occur due to artifacts confusing the algorithm.

pressure. After 6 weeks there was a transition to the other PAP therapy. The REMstar Auto M-series (Respironics Inc., New Kensington, PA, USA) was used during this study. Data were collected by objective and subjective measurements. Objective: polygraphy during both PAP treatment modes, and by downloading the data of the PAP device. Subjective: sleepiness (Epworth Sleepiness Score (ESS)), quality of life (disease specific: Quebec Sleep Questionnaire (QSQ), and generic: SF-36), preference for treatment mode, and tolerance.

RESULTS Thirty-nine OSAS patients were recruited of which already 21 completed the study. After 6 weeks with RAPAP, the median AHI decreased (1.9 [0.2 – 27.6] events\hour, p < 0.01) but did not differ compared to CPAP (p = 0.89). The compliance was similar between the treatment groups (CPAP: 6.6 [3.2 – 7.9] vs. RAPAP: 6.6 [4.3 – 7.9] hours/night, p = 0.13). The median of the mean applied pressure over 6 weeks RAPAP therapy was 8.4 [5.1 – 11.9] cmH2O and for CPAP 8.5 [6.0 – 11.9] cmH2O (p < 0.01). At the end of the study, patients expressed no significant preference for one or the other treatment. The subjective measurements ESS, SF-36 and QSQ showed improvement compared to baseline but no difference between treatment modes.

Polysomnography with CPAP titration. The intention of researchers is to determine and deliver the ‘right’ pressure to the individual patient within one night, but also from night to night. It remains to be examined whether optimization of the applied pressure can be attained by using the lowest possible minimum level and by limiting the maximum pressure to a different extent. The aim of this study was to investigate whether a new adjusted mode of APAP can improve patient adherence in comparison to fixed CPAP in present-day PAP therapy of OSAS patients.

Results of AHI at baseline and with the two different treatment modes.

The median of the mean device pressure with CPAP and RAPAP for 6 weeks.

CONCLUSIONS MATERIALS AND METHODS New diagnosed OSAS patients were selected for a single blind randomized cross-over trial. During 12 weeks patients received two different PAP therapies, CPAP and restricted APAP (RAPAP). Prior to starting up PAP therapy patients received a manual CPAP PSG titration. The titration night was used to set the CPAP and RAPAP. The RAPAP pressure sets the pressure level 2 cmH2O around the titrated

Analysis of 21 patients demonstrated that RAPAP and CPAP therapy have equivalent improvement in major outcomes of sleep apnea, including daytime sleepiness, impaired quality of life, respiratory disturbance index, compliance, and preference. RAPAP showed the advantage of delivering lower pressures during the therapy period. The new alternative RAPAP therapy seems to fit within the conventional CPAP treatment.

Medisch Spectrum Twente (Enschede), Pulmonology - M.M.M. Eijsvogel, F.H.C. de Jongh, M. Wagenaar (UT: W. Steenbergen)

SINGLE PULSE ELECTRICAL STIMULATION Quantitative EEG analysis of evoked responses in the epileptic brain Maryse van â&#x20AC;&#x2DC;t Klooster

INTRODUCTION In epilepsy surgery reliable pre-surgical markers of epileptogenic tissue are critical. The gold standard is seizure onset zone (SOZ) in long term intracranial EEG (electrocorticography, ECoG) recordings. Single Pulse Electrical Stimulation (SPES) can evoke late spike-like responses related to areas of seizure onset in the ECoG. Recently spontaneous high frequency oscillations (80-520 Hz) have been found that are related to spikes, but better characterize the epileptogenic cortex. We wanted to see whether time-frequency information of evoked responses by SPES could be characterized by a quantitative EEG analysis and enhance their specificity and clinical use.

METHODS ECoG data were recorded at a 2048 Hz sampling rate from 13 patients. SPES (10 stimuli, 1 ms, 4-8 mA, 0.2 Hz) was performed stimulating pairs of adjacent electrodes. Time frequency (TF) analysis based on Morlet wavelet transformation was performed in a [-1 s : 1 s] time interval around the stimulus and a frequency range of 10-520 Hz.

Significant (p=0.05) changes in power spectra averaged for 10 epochs were computed, resulting in Event Related Spectral Perturbation (ERSP) images. In these images TFSPES evoked late responses (>100ms after stimulation), in the range of 10-80 Hz for spikes, 80-250 Hz for ripples and 250-520 Hz for fast ripples, were scored by two observers independently. Sensitivity, specificity and predictive value of TF-SPES in the three frequency ranges were compared to seizure onset zone (SOZ) and post surgical outcome.

RESULTS In all patients, evoked responses included spikes, ripples and fast ripples. For the seizure onset zone the median sensitivity of TF-SPES evoked responses decreased from 100% for spikes to 67% for fast ripples and the median specificity increased from 17% for spikes to 79% for fast ripples. A median positive predictive value (PVV) for the evoked responses in the SOZ was found of 17% for spikes, 26% for ripples and 37% for fast ripples. A trend was observed that incomplete removal of fast ripples by resection was related to poor outcome.

CONCLUSION A wavelet transform based timefrequency analysis of SPES reveals evoked late responses in the frequency range of spikes, ripples and fast ripples. We demonstrated that TF-SPES evoked fast ripples are a promising new marker for delineation of the epileptogenic cortex.

Overview of the TF-SPES analysis of evoked late responses, showing ERSP images and the anatomical relation of these evoked spikes (1080Hz range),rRipples, (80-250Hz range) and fast ripples (250-520Hz range) with the seizure onset zone for a patient with temporal lobe epilepsy.

University Medical Center Utrecht, Neurology & Clinical Neurophysiology - F.S.S. Leijten, G.J.M. Huiskamp, C.H. Ferrier (UT: M.J.A.M. van Putten, A. van Cappellen van Walsum)

SYSTEMIC AND CEREBRAL HEMODYNAMICS IN ALZHEIMER’S DISEASE Aisha van den Abeelen INTRODUCTION As the leading cause of dementia, Alzheimer’s disease (AD), causes great social and financial burdens. To come with new ideas for diagnosing and treating AD, we studied the role of the vascular system in AD by studying the baroreflex functioning (BR). We studied whether BR is impaired in patients with AD and whether the value of BR can be used to distinguish AD patients from healthy elderly.

METHOD

Results:

Five-minute recordings of electrocardiography and photoplethysmographic finger systolic blood pressure were obtained in 18 patients with mild to moderate AD, aged (mean±standard deviation) 72±6 years and in 19 healthy elderly, aged 75±3 years. A 100 second period, free from artifacts and ectopic beats, was selected for analysis. The BR was quantified using a ARXAR model, which was proposed by Nollo et al. (2001). This model was applied to quantify the gain of the baroreflex regulatory mechanism. The BR was calculated in correspondence with the peak in the power spectra of the systolic blood pressure between 0.04 and 0.15 Hz, the frequency range in which baroreflex modulation of heart rate occurs.

RESULTS

Meetopstelling:

The BR was 6.4 ± 2.7 ms/mmHg in controls and 1.8 ± 1.5 ms/mmHg in AD (p<0.05). ROC curve analysis showed that the causal model estimation of BR distinguishes between healthy elderly and AD patients (sensitivity=89%, specificity=94 %, p<<0.01).

CONCLUSION Our study shows that the BR was significantly reduced in the AD group relative to the control group and that the causal model estimation of the BR has a great predictive value for AD. This suggests brainstem involvement in AD pathology or a reduction in the neural part of the reflex. The diagnostic and clinical implications of this reduced BR-index in preclinical and clinical AD need to be further explored.

Model used (Nollo et al. Causal linear parametric model for baroreflex gain assessment in patients with recent myocardial infarction. 2001):

Radboud University Nijmegen Medical Centre, Geriatrics - J.A.H.R. Claassen, J. Lagro (UT: M.J.A.M. van Putten, B.J. Zandt, A. de Keijzer)

PULMONARY DIFFUSION: SEARCHING FOR A NEW STANDARD Eline Oppersma

GOAL

RESULTS

Measurements of the diffusing capacity for carbon monoxide (CO) are variable. Especially when test results are around the lower limits of normal, diffusing capacity for CO cannot predict a physical limitation during exercise. Because of the high affinity of nitric oxide (NO) to bind to hemoglobin, the diffusing capacity for NO represents the true membrane diffusing capacity. The combination of the measurement of diffusing capacity for CO and NO can distinguish between the hemodynamic and the membranous component of the diffusing capacity. The aim of this study is to find out whether the diffusing capacity for NO (DL,NO) can be a more accurate predictor of the Alveolararterial (A-a) oxygen gradient at maximal exercise, compared to the diffusing capacity for CO (DL,CO). This relatively simple pulmonary function test could make the heavy maximal exercise test unnecessary in the future. Part of the variability in the measurement of DL,CO could be explained by the variable perfusion of the lungs. By measuring both DL,NO and DL,CO before and after maximal exercise, we expect to eliminate this variable perfusion from the DL,CO.

46 lung patients (median age 63.2 (22.1-83.3) years) performed a combined single breath DL,NO/DL,CO measurement and a maximal exercise test. Mean difference between pre and post measurement of diffusing capacity for NO was 1.29%R (SD 5.49%R) and for CO 1.97%R (SD 5.15%R). The A-a oxygen gradient at maximal exercise could be predicted based on the diffusing capacity for CO with an R2 of 68.2% and based on the diffusing capacity for NO with a coefficient of determination (R2) of 76.8%.

CONCLUSION 10 Minutes after maximal exercise, the measurement of diffusing capacity showed no difference compared to preexercise. Diffusing capacity for NO is a more accurate predictor of the A-a oxygen gradient at maximal exercise than diffusing capacity for CO.

METHODS All patients attending the pulmonary function department to undergo a maximal exercise test with blood gas analysis were asked to participate in this study and perform additional combined NO/CO diffusion measurements pre and maximal 10 minutes post the maximal exercise test. A model was constructed to predict the A-a oxygen gradient at maximal exercise based on diffusing capacity for NO and CO.

Scatter plot of Aa oxygen gradient on the yaxis and diffusing capacity for respectively NO and CO on the xaxis. Shaded grey area is the range where scatter of Aa gradient is most expanded with respect to the diffusing capacity.

Medisch Centrum Twente, Pulmonology - W.J.C. van Beurden, P.D.L.P.M. van der Valk, I. van der Lee (UT: F.H.C. de Jongh, A. de Keijzer)

ARTERIAL PRESSURE VARIATION AS A PREDICTOR OF FLUID RESPONSIVENESS DURING SPONTANEOUS BREATHING Dagmar Ouweneel RATIONALE In anesthesiology and intensive care medicine, intravenous volume is often administered to improve tissue oxygen delivery. Too little circulating volume (hypovolemia) can cause inadequate organ perfusion which may result in organ ischemia and organ failure. On the other hand, too much circulating volume increases the workload of the heart which may overload the heart, ultimately resulting in heart failure with development of pulmonary and peripheral edema that contributes to further tissue injury and organ dysfunction. In mechanically ventilated patients, arterial pressure variations have shown to be good indices to predict whether a patient will benefit from intravenous volume administration. However, in spontaneously breathing patients, arterial pressure variations have shown to be less predictive and the need for a good predictor of fluid responsiveness remains.

OBJECTIVE To investigate the effect of tidal volume, respiratory frequency and respiratory resistance on arterial pressure variations in healthy, spontaneously breathing subjects, to improve the predictive value of arterial pressure variation on fluid responsiveness in spontaneous breathing subjects.

METHOD Blood pressure, stroke volume, heart rate, cardiac output, tidal volume and respiratory flow were evaluated under conditions of normovolemia (supine resting position) and graded hypovolemia (simulated by passive 30 and 70° headup tilt positions in 10 healthy volunteers. Different breathing frequencies (spontaneous breathing, 6/min paced breathing and 15/min paced breathing) and the use of an inspiratory and expiratory threshold resistor were applied in each volemic state) in a randomized order. Arterial pressure

variations are calculated using several methods: several time domain calculations and calculations using the frequency domain. Subjects with a decrease in SVI ≥ 15% were classified as responders and SVI<15% as non-responders. Receiver operating characteristics were generated and area’s under the ROC were calculated and compared between different calculation methods.

RESULTS In relation to spontaneous breathing without the use of a resistor, the relation between the change in stroke volume index (SVI) and pulse pressure variation (PPV) increases during 6/min paced breathing and by using either an inspiratory or expiratory threshold resistor. During spontaneous breathing without the use of a threshold resistor, arterial pressure variations have low predictive values (27% sensitivity, 94% specificity). When 6/min paced breathing is applied in combination with an inspiratory or an expiratory resistance, the relation increases by means of higher R2 and an increase in slope. This results in better predictive values when using an expiratory resistor for both PPV (85% sensitivity, 100% specificity) and systolic pressure variation (SPV) (sensitivity 92%, specificity 94%). Different calculation methods for PPV and SPV did not disclose significant differences in area under the receiver operating curves.

CONCLUSION In this study, inspiratory and expiratory threshold resistors and 6/min paced breathing magnified pulse pressure variation in spontaneously breathing healthy subjects during simulated hypovolemia. During 6/min paced breathing in combination with an inspiratory or expiratory resistor, PPV and SPV appeared to be good predictors of a decreased stroke volume index in healthy subjects. ROC curves comparing the ability of PPV and SPV to discriminate responders and nonresponders to volume expansion.

Academic Medical Center (Amsterdam), Internal Medicine & ICU - J.J. van Lieshout, B.E. Westerhof (UT: M.J.A.M. van Putten, B. Lansdorp, A. de Keijzer)

MUSCLE AGEING ASSESSMENT USING WRIST NEUROMECHANICS Marjon Stijntjes

Sarcopenia, the age-related loss of muscle mass, is of increasing interest. One of the reasons is its strong association with functional decline. Many fundamental questions about this relation remain unanswered. Muscle power, which is the product of muscle strength and movement velocity, may be an important functional aspect in the loss of functionality. Several daily activities require the generation of muscle strength and velocity, for example, getting out of a chair. However, measuring muscle power is difficult. Force and velocity needs to be adjustable for the assessment of the maximal muscle power of a subject. Furthermore, several underlying determinants of muscle power should be measured to understand the origin of agerelated changes on muscle power. The goal of this study was to develop, implement and evaluate a method for the measurement of muscle power and an assessment method to link muscle power to main underlying determinants. Muscle power of the flexor muscles of the hand was measured in two different groups, using a wrist manipulator. The first group consisted of fifteen healthy young subjects (aged 20 - 30 years) and the second groups of fifteen healthy old subjects (aged 70 - 80 years). Different loading conditions were applied to measure muscle power at different forces and velocities. Muscle power was measured during voluntary contraction of a relaxed muscle (voluntary muscle power) and after release of a pre-tensed muscle (responsive muscle power, which was measured at different torque levels). Primary outcome parameters were maximal muscle power and the corresponding angular velocity. Secondary outcome parameters were the underlying determinants of muscle power that were assessed, i.e. muscle mass of the dominant arm, muscle activation dynamics and muscle fiber typing. The influence of muscle fiber typing was aimed to be assessed by measurements of short-range stiffness. Furthermore, handgrip strength and maximal voluntary contraction of the flexor muscles of the hand were secondary outcome parameters. Maximal voluntary muscle power of the older females was lower compared to the younger females (p=0.003). The angular velocity at maximal voluntary muscle power was not different between young and old subjects. For the higher torque levels, maximal responsive muscle power was lower for old females compared to young females. Among males, maximal responsive muscle power was higher for the older subjects. No differences between young and old subjects were found according to the velocity at maximal responsive muscle power. Muscle mass of the dominant arm was lower for the older females than for the younger females (p=0.018) 22

and muscle activation dynamics was slower (p<0.001). No differences in these parameters were found among males. At higher torque levels, short-range stiffness was higher for old females compared to young females and lower for old males compared to young males. Handgrip strength was lower for old subjects compared to young subjects (p=0.002). Lower maximal voluntary contraction was found for old subjects than for young subjects after stratification for gender (p=0.027 and p=0.025 for males and females, respectively). This study showed that the developed set of measurements is suitable for measuring muscle power and its underlying determinants. Differences between young and old subjects in maximal muscle power were dependent on the functional condition at which muscle power was measured. Therefore, measuring muscle power at different functional conditions is required to get insight into the consequences of muscle ageing on physical performance. Furthermore, differences between young and old subjects in muscle power were found to be gender-specific. This could be explained by the different findings among males and females in main underlying determinants of muscle power. Future research is necessary on the evaluation of these gender-specific findings.

Experimental setup of the wrist manipulator. The subject had to hold a handle, which was connected via a lever to the axis of an electrical motor. The elbow was fixed with stiff rubber clamps. Polypropylene (PP) foam malls were used to stabilize the radial and ulnar styloid processes. The hand was fixed to the manipulator handle with a PP foam mal and tie wraps.

Leiden University Medical Center, Rehabilitation Medicine - C.G.M. Meskers, E. de Vlugt, A.B. Maier, J.H. de Groot (UT: H. van de Kooij, A.A. Stoorvogel)

COMPUTER ASSISTED GRADING OF EEG IN POSTANOXIC PATIENTS AFTER CARDIAC ARREST Fokke van Meulen PURPOSE Neurologic recovery after cardiac arrest is primarily determined by the extent of postanoxic encephalopathy (PAE). The EEG correlates with the neurological outcome; however early prognostication for individual patients is difficult. Furthermore, visual interpretation is time consuming and only feasible for well-trained neurologists. The purpose of this study is to evaluate the prognostic value of continuous EEG (cEEG) monitoring and the uses of quantitative EEG (qEEG) in patients after cardiac arrest suffering from postanoxic coma.

METHODS During a prospective study, 56 patients admitted to the ICU of the Medisch Spectrum Twente for treatment with therapeutic hypothermia (TH) after cardiac arrest were included. cEEG registrations were made during the first five days of admission or until discharge from the ICU. Five minute EEG epochs were automatically selected every hour during the first 48 hours after resuscitation and every two hours during the rest of the registration. All epochs were blinded and randomized before they were visually scored. Additionally, the epochs were automatically classified and the Shannon entropy, signal power and frequency distribution were calculated. A recovery function, based on the different automated analysis methods is developed. Neurological outcome was determined based on the best achieved Cerebral Performance Category (CPC) score within 6 months.

RESULTS Twenty-seven out of 56 patients (48%) had good neurological outcome (CPC1-2). Visually differences between EEG rhythms in the group of patients with a bad prognosis and a good prognosis can be seen. The presence of a diffuse slowed EEG rhythm 12 hours after cardiac arrest has sensitivity for good prognosis (CPC1-2) of 40% and a specificity of 100%. The presence of an iso-electric, low voltage or burst suppression pattern has a sensitivity for bad prognosis (CPC3-5) of 95% and a specificity of 96%. Using multiple qEEG features provides the ability to distinguish within an automatically classified category. The recovery function - based on the most distinctive features - is defined, which value correlates with the neurological outcome of a patient.

Recovery Function (RF) values of all epochs. The green and red dots are the median values of patients with good and poor outcome, respectively. The corresponding coloured areas are the 100% ranges of the RF values. The grey area is where the ranges overlap each other. Through the median values exponential functions were fitted.

CONCLUSION EEG monitoring and qEEG allow early prognostication in patients with TH after cardiac arrest. A function is developed which value correlates with the neurological outcome of a patient. Bad as well as good neurological outcome can be predicted using the new recovery function. The recovery function shows remarkable differences between the time constants of the group of patients with a bad outcome and the group of patients with a good outcome.

Medisch Spectrum Twente (Enschede), Neurology & Clinical Neurophysiology - M.J.A.M. van Putten (UT: T. Heida, M.C. Cloostermans, B. ten Haken)

LONGITUDINAL EEG STUDY ON BRAIN 足PATTERNS DURING MOTOR IMAGERY IN THE ACUTE STROKE PATIENT Rens Verhagen INTRODUCTION Recent developments in rehabilitation therapy after stroke give rise to the question if motor imagery therapy can be a valuable additive to standard stroke rehabilitation therapies. However, studies on this subject do not show a convincing positive influence on rehabilitation outcome. The effect of motor imagery therapy could be improved by providing feedback to the patient in the form of a brain computer interface (BCI). This study researches the brain patterns that can be measured with EEG in the acute phase after stroke to be able to create a BCI in the future which can adequately be controlled by an acute stroke patient.

METHODS Four follow up EEG measurements are performed in ten acute (sub)cortical stroke patients in the first four months after stroke. For every measurement EEG parameters based on event related desynchronization (ERD) are calculated using both alpha and beta rhythms as the sensorymotor rhythm and patients are physically examined to test their recovery using the NIHSS score and the Fugl-Meyer score. Correlations between the amount of ERD or the size of the ERD area and these functional scores are calculated.

correlations are found between FM scores and the alpha and beta ERD percentage measured over the laesional hemisphere (R=-0.827, p<0.001 and R=-0.809, p<0.001 respectively). Results similar to these last two correlations are found when using the NIHSS score instead of the FM score to calculate correlations.

DISCUSSION A remark should be made on the significance of these correlations, these might be exaggerated because the correlation calculation does not account for the clustering of measurements within individual patients. The patterns that are found can be related to patterns found in previous studies and can be explained by underlying recovery processes like resolution of diaschisis and tissue repair leading to neuronal and map plasticity.

CONCLUSION EEG measurements during motor imagery can show brain patterns that correlate with the recovery of acute stroke patients. These brain patterns might be used in the future to create a BCI that might be able assist in stroke rehabilitation.

RECOMMENDATIONS RESULTS Over the whole group only a weak negative correlation is found between the FM score and the size of the alpha ERD area over the contralaesional hemisphere (R=-0.528, p<0.05). In the cortical stroke subgroup the same weak negative correlation is found between the FM score and the size of the alpha ERD area over the contralaesional hemisphere (R=-0.549, p<0.05) and strong positive

It is recommended for future studies on this subject to focus on the cortical stroke patient, since this subgroup shows the most promising correlations. Furthermore a greater number of patients should be included, the algorithm calculating the size of the area showing ERD should be improved and extra EEG measures like the brain symmetry index should be included to verify the found correlations or find other brain patterns described in previous studies.

An example of the set up of the beginning of one experimental trial after the selection of an optimal baseline video. This picture shows the variation between baseline and active period being guided by the baseline and active videos. The trial always starts with a baseline video (for this subject the optimal baseline video is two balls moving in the center of the screen) and shows left or right hand grasping in a random order. Each trial has sixteen active periods (eight left handed and eight right handed) and sixteen preceding baseline periods.

Medisch Spectrum Twente (Enschede), Neurology & Clinical Neurophysiology - M.J.A.M. van Putten (UT: T. Heida, A.A. Stoorvogel, C.Tangwiriyasakul)

A NOVEL AMBULANT MONITORING SYSTEM FOR LOWER EXTREMITY FRACTURE HEALING Development and performance evaluation of the SensiStep Michelle Meeks BACKGROUND Partial weight bearing is often instructed in patients suffering from a lower limb fracture. However, patient compliance is low, with overloading or underloading of the affected leg as a result. Continuous measurements of weight bearing and feedback to the patient could improve the compliance. SensiStep was developed to assess weight bearing and provide feedback to the patient and healthcare provider in a real-time, ambulant and long-term setting. Objective: To investigate the potential of SensiStep in a fracture rehabilitation setting.

METHODS First, a literature study was performed to determine how accurate the commercially available load measuring systems are. Second, clinically needed accuracy, desired feedback method and functionalities of SensiStep were assessed by experienced senior clinicians. Validation tests were carried out to assess the functioning of SensiStep in various conditions. Dynamic and static loading tests, hysteresis, off centre and angle measurements and temperature tests were carried out. The dynamic and static tests were carried out with increasing loads from 10 to 100 kilograms during ten sessions and a constant load of 100 kilograms for 2 hours. Hysteresis was determined from the dynamic tests. A load of 100 kg was exerted at 1 cm from the centre and a wedge of 5° was placed under the sensor when loaded in the centre. Temperature tests were carried out at 50°C. In addition, subject tests were carried out on the Single Belt3D treadmill and on a Seca weighing scale. Walking speeds from 0.5 to 5.0 km/h were used in the treadmill test. An embedded sensor and bare sensor were used in the weighing scale test.

RESULTS

during the weighing scale tests with a bare sensor and an embedded sensor as well as during the walking test, the loads were lower with respectively 40%, 50% and 70% of the true value. Measurements with healthy test subject showed comparable results; peak loads down to 30% of the true peak value during walking and 70% when standing on an embedded sensor.

CONCLUSION SensiStep has a good clinical potential. However, the clinically needed accuracy is currently not met. Limitations of the system are the underestimation of the peak load and off centre deviations. A sensor re-design is needed.

Figure displays the SensiStep sandal with the SensiStep sensor. Which can be placed in the sandal as indicated. The round area on the sensor is the actual force measuring area.

Three load measuring systems are commercially available. Pedar is the most accurate, but still has a error up to 17% error and systematically underestimates the load. Eleven clinicians participated generally accepted an accuracy level of 10%. Light or sound in combination with vibration feedback are the preferred feedback method. Besides the peak load, parameters such as load distribution and number of steps were desired. SensiStep could be calibrated via gain and baseline tuning. Bench press tests demonstrated that the repeatability of the SensiStep was high (maximum SD in gain: 0.017) and hysteresis was only 1 kg. The gain of SensiStep appeared stable after a temperature increase, angle measurements also didn’t affect the gain. Off centre measurements resulted in deviations up to 32% of the centre output. SensiStep underrated the force in patients 25

University Medical Center Utrecht, Traumatology - T.J. Blokhuis, H.R. Holtslag (UT: H.J. Hermens, L.M.G. Vrijhoef-Steuten)

BRAIN SYMMETRY INDEX Clinical evaluation of the Spatial and Temporal Brain Symmetry Index (BSI) Marjolein van Bloem

SUMMARY Objective: Asymmetry in an electroencephalogram (EEG) maybe an important indicator for a non-healthy brain. The interpretation of EEG asymmetry is usually performed by visual analysis. To assist visual interpretation the spatial brain symmetry index (sBSI) and the temporal brain symmetry index (tBSI) were introduced, to detect right-left asymmetry and asymmetry over time respectively. Although both indices have found applications for various clinical problems, few research has been done regarding their reliability in terms of sensitivity and specificity. In this thesis reliability of sBSI and tBSI is evaluated for different patientgroups. Also a new method to quantify temporal asymmetry, the minimal BSI (minBSI) is introduced.

METHODS The reliability of the sBSI is retrospectively evaluated in 61 patients performing a Wada-test. For the tBSI and minBSI reliability is retrospectively evaluated in 28 patients for EEG signals recorded during hyperventilation. The reliability of all indices is expressed as the area under their ROC-curves (AUC).

RESULTS The sBSI and the pair wise derived BSI with changed absolute sign position (pdBSI-abs) showed best reliability

during the Wada-test with an AUC of 0.87 and 0.86 respectively. Making them both adequate to assist visual EEG interpretation thereby reducing the subjectivity of the Wada-test. An important finding is that the sBSI response during the Wada-test depends on the EEG signal frequency. It is therefore important to realize for which frequency band assistance from the spatial BSI is needed during visual assessment. A promising tool to support sBSI interpretation is a newly introduced BSI-mapping interface, which visualizes the BSI response for four different frequency bands. The AUC for the tBSI and minBSI during hyperventilation EEG signals were respectively 0.54 and 0.79. The low AUC for tBSI is due to the use of a fixed correction factor and the use of the absolute value in its computation. It would be better to omit the absolute value and to calculate an optimal correction factor for each individual patient, but this remains a challenge for the future.

CONCLUSIONS sBSI and pdBSI-abs are useful methods to detect hemispheric asymmetry during a Wada-test and can assist in visual EEG interpretation. The tBSI is not an accurate test to detect temporal asymmetry. A promising new method seems to be the minBSI.

Temporal Brain Symmetry Index (tBSI) and minimal Brain Symmetry index (minBSI) during hyperventilation for two patients. The tBSI (A & B) and minBSI (C & D) are plotted versus time (one page is 10 seconds). For the calculations of the tBSI an offset correction factor of 0.10 is used. 26

Maastricht University Medical Center, Clinical Neurophysiology - V. van Kranen-Mastenbroek, J.P.H. Reulen (UT: M.J.A.M. van Putten, T. Heida)

DEVELOPMENT OF A NEW TECHNIQUE FOR THE MEASUREMENT OF CEREBRAL BLOOD FLOW IN PATIENTS WITH ACUTE BRAIN INJURY AT THE INTENSIVE CARE UNIT Helga Blauw

Neurological care at the intensive care unit (ICU) aims to minimize secondary brain injury in patients with acute brain injury. Because adequate cerebral blood flow (CBF) is a prerequisite for the recovery and survival of brain tissue in these patients, it is desired to monitor the effect of interventions on the CBF. In addition, autoregulatory mechanisms of CBF may be affected in the damaged brain. However, bedside measurement of CBF is not possible at this moment. General systemic parameters and brain specific parameters related to CBF do not reliably reflect changes in cerebral perfusion. The aim of this research project is therefore to develop a new technique for the measurement of CBF in patients with acute brain injury at the ICU. Requirements for the new measurement technique were defined: the technique had to reflect changes in CBF, be minimally invasive, safe and repeatable at the bedside. Techniques that have been applied in the clinic or in research settings to measure the CBF or related parameters in patients with acute brain injury do not fulfill these requirements. However, contrast enhanced ultrasound is promising because it can be used bedside and is noninvasive. Also a broad search of flow measurement techniques in other medical and industrial disciplines was performed. These techniques are not considered to work for CBF measurement. Therefore, contrast enhanced ultrasound was selected for further investigation.

The refill kinetics method is promising because it allows semi-quantitative measurement of the microcirculatory blood flow in different brain regions. Further investigation should address the practicability of this method at the ICU.

Refill kinetics method. After destruction of the microbubbles in the imaging plane the measured acoustic intensity exponentially increases to the maximum intensity. The plateau echo enhancement is related to contrast blood volume or microvascular cross sectional area and the rise rate is related to blood flow velocity.

Contrast enhanced ultrasound uses microbubbles that are injected intravenously as contrast agent. The two main approaches to measure the CBF are the bolus kinetics and refill kinetics. Although the bolus kinetics approach has been more extensively studied than the refill kinetics, its parameters were found to be less useful for the desired application at the ICU than the refill kinetics parameters. Therefore, the refill kinetics was chosen to be the best basis for further developments. For the new measurement technique, it was proposed to normalize the measured acoustic intensity with respect to the acoustic intensity measured in a region of interest located in an artery. This will minimize the variability in the refill kinetics parameters that reflect cross sectional area and blood flow and it may also extend the time following a bolus injection during which measurements can be performed.

Radboud University Nijmegen Medical Centre, ICU - C. Hoedemaekers (UT: B. Lansdorp, W. Steenbergen)

WAVELET-BASED MARKERS OF VENTRICULAR FIBRILLATION IN PREDICTING DEFIBRILLATION OUTCOME Stefan van Duijvenboden BACKGROUND

CONCLUSIONS

Out-of-hospital cardiac arrest (OHCA) is a leading cause of death in Europe. Ventricular fibrillation (VF) is the initial rhythm in 30-40% of the OHCA patients. A substantial number of shocks is not successful in terminating VF. Characterization of the VF ECG morphology using amplitude and frequency measures can predict defibrillation success, but the predictive value is not sufficient enough to be clinically relevant. The VF signal is chaotic and not periodic, therefore we employed the continuous wavelet transform (CWT) which performs simultaneous analysis in both time and frequency. Visual inspection revealed stronger irregularities in VF signals associated with successful defibrillation. A numerical procedure to compute the degree of irregularity using the CWT was employed to characterize the VF ECG morphology. We hypothesized that this method could predict defibrillation outcome with more accuracy.

The predictive value of the studied amplitude, frequency and wavelet features are not reliable enough to predict defibrillation outcome. Characterization of local irregularity found in the VF ECG did not improve prediction of ROOR or termVF. The relation between local regularity and shock outcome had never been studied before. It was found that not all results reflected the actually sharpness of the irregularities. This method may therefore be less suited for analysis of the VF waveform.

METHOD AND RESULTS We included 104 OHCA patients with VF as initial recording rhythm. Threesecond ECG segments prior to shock and free of CPR artefact were collected. VF segments before initial shocks (n = 82) and before the first five shocks (n = 231) were selected for analysis. The predictability of shock success was investigated for two definitions: return of organized rhythm (ROOR) and termination of VF (termVF). VF signals were analyzed retrospectively using existing amplitude, frequency and wavelet methods derived from literature. The methods included mean amplitude, median slope, peak-power-frequency (PPF), centroid frequency (CF) and the amplitude spectral area (AMSA), center scale (CS), scale distribution width (SDW) and wavelet entropy (ENTR). Subsequently, we employed a method to measuring irregularities using the local maxima of the wavelet transform modulus. The degree of irregularity was computed as the Lipschitz exponent. The association between the studied signal characteristics and defibrillation outcome was stronger for ROOR than for termVF. The strongest predictors of ROOR were median slope (ROC AUC=0.703) and AMSA (ROC AUC=0.682). The method to measure local irregularities did not predict shock outcome and performed less than amplitude and frequency measures.

Radboud University Nijmegen Medical Centre, Cardiology - J.L.R.M. Smeets, J.L. Bonnes (UT: C.H. Slump, G. Meinsma)

PREDICTING THE RESPONSE TO FLUID ADMINISTRATION DURING PRESSURE SUPPORT VENTILATION Eva Merckel RATIONALE Fluid administration is commonly performed in critically ill patients, but only around 50 percent of the patients will increase their systemic blood flow in response to volume expansion. Dynamic parameters, like the pulse pressure variation (PPV) and systolic pressure (SPV), predict the cardiac output response to a fluid challenge in patients during controlled mechanical ventilation. But up to now studies have failed to demonstrate a dynamic parameter which can predict the response to volume expansion in mechanically ventilated patients with spontaneous respiratory movements.

OBJECTIVE To investigate the possibility to predict fluid responsiveness during pressure support ventilation. Methods: In a retrospective study ventilation and blood pressure signals were analyzed to acquire more insight into the cardiopulmonary interactions during pressure support ventilation. Thereafter a prospective interventional study was conducted in nine patients ventilated with pressure support. Four minutes before fluid loading central venous pressure (CVP), arterial blood pressure (ABP), electrocardiogram (ECG), airway flow (AWF) and airway pressure (AWP) were recorded at baseline and increased pressure support level. PPV, SPV, tidal volume (TV) and change in central venous pressure (â&#x2C6;&#x2020;CVP) were calculated during these ventilation levels. Cardiac output was measured with the Nexfin before and after a fluid challenge.

Receiver operating characteristics curve analysis was used to evaluate the predictive value of the calculated indices on volume responsiveness.

RESULTS The retrospective study showed that patients ventilated with pressure support can be divided into two groups. In one group an increase in pleural and central venous pressure during pressure support inspiration was observed. The cardiopulmonary interactions were similar to the interactions during controlled mechanical ventilation. In the other group the pleural and central venous pressure decreased during inspiration. Regression analysis showed that PPV and the decrease in pleural pressure were linear correlated, and the heart lung interactions were similar to the interactions during spontaneous breathing. In the prospective study a threshold PPV, SPV and â&#x2C6;&#x2020;CVP value of respectively 8.5%, 5.6% and 3.3 mmHg predicted fluid responsiveness with a sensitivity and specificity of 100% in the patient group with an increase in central venous pressure during pressure support inspiration. In patients with a decrease or both an increase and decrease no predictive value was found.

CONCLUSION In patients with only an increase in central venous pressure PPV, SPV and the increase in CVP can distinguish responders from non-responders during pressure support ventilation. However in all other patients we were not able to predict the response on fluid administration.

Pressure signals during pressure support ventilation. Left: Increasing pleural and central venous pressure during each inspiration. Right: Decreasing pleural and central venous pressure during each inspiration

Radboud University Nijmegen Medical Centre, ICU - J.Lemson, J.M.D. van den Brule (UT: B. Lansdorp, F. van der Heijden)

OPTIMIZATION OF CARDIAC RESYNCHRONIZATION THERAPY IN CLINCAL PRACTICE DURING EXERCISE Marleen Molenaar AIMS

CONCLUSION

One third of the patients treated with cardiac resynchronization therapy (CRT) do not experience noticeable improvement of cardiac function. Proper timing of the delay between atrial and ventricular pacing pulses (AV-delay) is of major importance for the created stroke volume and the treatment effect of CRT. In this study the feasibility of the Nexfin in optimization of AV-delay during exercise based on stroke volume was assed (a). The relation between heart rate and optimal AV-delay was assessed to create an optimal AV delay/ HR model (b). The surface ECG is analysed to assess whether a relationship exists between QRS-width and optimal AV-delay (c). A graphic user interface (GUI) for use during optimization is created.

This study is the first step in clinical application of the Nexfin in AV-delay optimization during exercise. The Nexfin is found feasible for optimization of AV-delay during exercise. In every patient AV-delay in rest and during exercise should be optimized individually.

METHODS AND RESULTS Thirty-one patients implanted with a CRT device in the last four years participated in the study. During rest and in exercise, stroke volume (SV) was measured using the Nexfin device for several AV-delays. The optimal AV-delay in rest and in exercise was determined using the least squares estimates (LSE) method. Optimization creates a clinically significant improvement in stroke volume of 10% (mean). The relation between heart rate and the optimal AV-delay was patient dependent. No relationship was found between QRS-width and optimal AV-delay. A graphic user interface, which enables a fast, correct and standardized optimization, was created.

Medisch Spectrum Twente (Enschede), Cardiology - J.M. van Opstal (UT: M.J.A.M. van Putten, B. ten Haken, W. Wesselink)

MEASURING OSAS SEVERITY WITH AN MRA WITH INTEGRATED SENSOR Proof of Concept Rob Hartman GOAL

CONCLUSION

Nowadays titration of mandibular advancement during polysomnography (PSG) or polygraphy (PG) is used to optimise treatment of obstructive sleep apnea syndrome (OSAS) with a Mandibular Repositioning Appliance (MRA). Parameters such as the apnea-hypopnea index (AHI), arousal index and snoring are used as a measure for treatment success. During PSG the constant presence of a trained individual who can monitor for technical adequacy, patient compliance and relevant patient behaviour is necessary according to the guideline [Epstein (2009)]. This way ensuring of the therapeutic effect of the MRA becomes very time-consuming and expensive. This has already improved with the advent of the unattended home testing with a NOX-T3 portable sleep monitor, the so called PG. Another downside of the PSG and PG is that they are only conducted during a single night and so the measurement may not represent a usual night of sleep of the patient. Also the patient compliance is unknown for the nights without a PSG or PG. Therefore a new measurement system is needed to help in the diagnosis of OSAS in patients with MRA therapy. The goal of this proof of concept study is to find a sensor that can be integrated in the MRA and can measure as many of the following parameters as possible: breathing patterns, snoring, movement activity, patient position and compliance.

Although the amount of patients used in this proof of concept study was low, the first results look promising. It can thus be concluded that it is plausible to measure therapy effect of the MRA with an accelerometer in the MRA. A first step in further development of this new measurement system is to improve the matlab detection scripts and the SoS of the accelerometer data.

METHODS Five patients that were diagnosed with OSAS and by whom the therapeutic choice fell on an MRA were included in this study. An accelerometer was placed inside the MRA by the dentist. The accelerometer then measured for one night during which also a PG was conducted. Matlab was used to find the parameters in the accelerometer data and to compare its outcome with that of the PG. Results Measuring compliance and determining movement activity and the position of the head was possible in all five patients. Detection of snoring was possible in only three of the patients in which an average of 83% of actual snores was detected by the MRA. The data of the two remaining patients could not be used because in one patient the accelerometer data had such a large noise band that snoring was overruled and another patient stopped snoring with the use of the MRA. The detection success depended on the value of the Sum of Squares (SoS). Breathing could be extracted from the accelerometer signal in 3 of the 5 patients.

Medisch Spectrum Twente (Enschede), Pulmonology - M.M.M. Eijsvogel (UT: F.H.C. de Jongh, E. Droog)

THE INFLUENCE OF SPINAL CORD STIMULATION ON PAIN AND PAIN PROCESSING Marjanne Bom INTRODUCTION Spinal Cord Stimulation (SCS) is treatment for patients with severe chronic pain. During SCS, the spinal cord is electrically stimulated. Recently De Ridder et al. (Neurosurgery, 66:986-90, 2010) developed burst SCS, in which pulse trains instead of the conventional single pulses (tonic SCS) are delivered. In patients with failed back surgery syndrome (FBSS) De Ridder et al. showed lower pain scores in burst stimulation than in tonic stimulation (Visual Analog Score (VAS) axial pain: tonic 4.42, burst 1.0; limb pain: tonic 3.13, burst 0.25). Furthermore, all patients preferred burst stimulation. We studied whether burst reduces pain compared to tonic and no SCS, whether patients preferred burst stimulation, whether physical performance increased during burst SCS, and whether there are certain patient characteristics that can predict success with burst stimulation.

explanation is that our patients are habituated to SCS, for they generally had SCS for already several years. Predictive for burst preference is the absence of paresthesias in the painful area. However, only a small number of patients showed this absence, which limits its reliability. Furthermore, some of the variables were not specific. Better variables and more data would increase the sensitivity and reliability of predicting factors. Neurophysiologically, we probably also have stimulated AÎ˛fibers. This means that all differences found later than the P50 represent a mix of pain processing and tactile processing. There were many missing data for earliest responses. Other approaches may suit the analysis of IESEPs better.

Neurophysiologically, some studies showed enhanced processing of pain in patients with chronic pain. In addition, SCS might influence the pain processing. Therefore, we also studied whether there are differences in pain processing as cause of pain level or stimulation setting in patients during tonic, burst or no stimulation and compared this to participants without pain.

METHODS In total 47 patients, mainly diagnosed with FBSS or diabetic neuropathy, participated in a two week trial period with burst stimulation. During tonic (baseline), burst (two weeks) and no stimulation (at least 12 h) patients filled in questionnaires. Pain processing was assessed by evoked potentials of intra-epidermal stimulation (IES-EPs). Furthermore, 14 controls participated in IES-measurements. IES was applied at the dorsum of the right hand. The P50 and N90 in C1-Fz, N150 and P200 in C5-Fz and P100 and P300 in Cz-M1M2 were manually identified and analyzed with mixed models. In addition, a subtraction analysis was performed. Logistic regression was used to find a predictive model for the success of burst stimulation. Success was defined as 33% pain reduction compared to tonic stimulation and as preference for burst stimulation.

RESULTS AND DISCUSSION We found a significant clinical effect of burst stimulation, however, success is less than previous reported. This also holds for our subgroup of FBSS patients. A possible

Pain scores in the different stimulation settings. All patients with three measurements included (N=26)

CONCLUSION The success of burst stimulation reported previously, was not reproduced and it is difficult to predict who will have success of burst stimulation. Thus far, trial periods of burst SCS remain needed. Neurophysiologically, patients showed no enhanced processing compared to participants without pain and therefore, there was also no normalization of processing after pain relief. Within patients pain level and stimulation settings possibly have influence on IES-EPs.

MST - Clinical Neurophysiology: M.J.A.M. van Putten, C.C. de Vos (UT: R.H.J. van der Lubbe, A.A.Poot)

DYNAMIC CARDIOVASCULAR INDICES AS PARAMETERS OF BRAIN PERFUSION AND OXYGENATION IN RESPONSE TO CENTRAL BLOOD VOLUME DEPLETION. Anne-Sophie Bronzwaer

BACKGROUND

CONCLUSION

Severe hypovolemia is characterized by a critical reduction in central blood volume. Intravascular fluid administration serves as the first-line intervention. Variations in arterial pressure (e.g. pulse pressure variation (PPV) and systolic pressure variation (SPV)) are being introduced in clinical medicine as potentially useful tools to guide volume administration. Although improvement of tissue perfusion and oxygenation as the actual therapeutic endpoints, cardiac stroke volume (SV) is presently the surrogate endpoint of a fluid challenge. The objective of this study was to delineate the relationship between arterial pressure variations and parameters of regional brain perfusion and oxygenation under conditions of graded normo- and hypovolemia in healthy spontaneously breathing subjects.

Arterial pressure variations tightly relate to MCAVmean, as measure for brain perfusion, in graded hypovolemia during the SB condition. Clinically more interesting is the demonstration that arterial pressure variations are able to predict changes in MCAVmean with the same sensitivity and specificity as when they predict changes in SV. However, in contrast to our expectations, enlargement of arterial pressure variations by PB through an inspiratory resistance weakens these relationships and predictive values considerably.

METHODS In 14 healthy subjects we followed mean arterial pressure (MAP), PPV, SPV, heart rate (HR), SV, cardiac output (CO), end-tidal CO2 (PetCO2), mean middle cerebral artery (MCA) blood velocity (Vmean) and normalized near-infrared spectroscopy determined cortical brain oxy-hemoglobin ([cO2Hb]), deoxy-hemoglobin ([cHHb]), and totalhemoglobin [ctHb] during graded hypovolemia by 30° and 70° passive head-up tilt (HUT). Given reports that an impedance threshold resistance enhances variations in pulse and systolic pressure due to enlargement of pleural pressure changes, the subjects were tested under two breathing conditions (spontaneous (SB) and paced breathing (PB) at 6∙min-1 through an inspiratory resistance).

RESULTS From supine to 70° HUT, MAP remained constant, SV decreased (-28%) and HR increased (32%) with a slight reduction in CO (-7%). PPV (91%) and SPV (83%) increased in response to 70° HUT. From supine to 70°, MCAVmean (-17%) and [cO2Hb] (-4.3 μmol∙L-1) decreased whereas [cHHb] and [ctHb] remained constant. Following tilt-back all values returned to baseline values with an overshoot of [cO2Hb] and [ctHb]. MCAVmean correlated in a linear fashion to SV (R2=0.52, p<0.0001) and arterial pressure variations (PPV: R2=0.46, p<0.0001; SPV: R2=0.45, p<0.0001). PPV and SPV (cutoff threshold >15% and >12%, respectively) predicted ΔMCAVmean during SB with higher accuracy compared to PB (sensitivity 58% and 67% versus 29 and 29%, respectively).

There is a strong relation between ΔMCAVmean and ΔSV as well as between ΔMCAVmean and ΔPPV/ΔSPV. The application of an inspiratory resistance together with a paced breathing frequency of 6∙min-1 weakens these relationships considerably. *p<0.0001

Academic Medical Center (Amsterdam), Internal Medicine & ICU - J.J. van Lieshout, B.E. Westerhof (UT: B. Lansdorp, M.J.A.M. van Putten, H.F.J.M. Koopman)

VAGUS NERVE STIMULATION Side Âeffects in epilepsy during exercise and the bronchodilating effect Daphne Mulders

In epilepsy, vagus nerve stimulation (VNS) aims to reduce seizure frequency or even completely avert seizure occurence. Beside positive effects, certain side effects are reported, including dyspnea and bradycardias. Furthermore, some patients experience no side effects from VNS during rest, but they mention a decrease in physical condition during exercise, reported as breathlessness, with an uncertain cause. Furthermore, VNS is considered for treating or preventing symptoms of reactive airway diseases, such as asthma and COPD. Studies showed that invasive stimulation of the vagus nerve could cause improvement of lung function and dyspnea, which led to the development of a transcutaneous VNS: AlphaCore. This project aimed to, on the one hand, investigate the phenomenon of breathlessness during exercise in epilepsy patients with VNS and, on the other hand, the relief of bronchoconstriction due to the use of the AlphaCore stimulator in asthma patients. Furthermore, this paradox of effects of VNS raises question about how stimulation of the vagus nerve can result in these contradictory effects. An attempt at explaining this phenomenon was made. First, ten epilepsy patients, either with or without reported side effect during exercise were measured during rest and exercise, while monitoring cardiorespiratory parameters. Analysis showed that VNS decreased tidal volume and breathing frequency, and increased inter-beat-interval,

during rest and exercise. No difference was found between the effect during rest and exercise, nor between the two subgroups. Next, thirty patients with positive metacholine challenge tests (MCT) (FEV1 decrease â&#x2030;Ľ 20%) were treated with either salbutamol inhalations or AlphaCore stimulation. For 15 minutes after treatment, cardiac parameters and FEV1 were measured. Patients treated with the AlphaCore, whose FEV1 had not improved to > 85% after 6 minutes of treatment also received salbutamol. Although AlphaCore stimulation aided in the recovery of FEV1, patients who received salbutamol recovered faster. Patients who received both AlphaCore stimulation and salbutamol recovered best. Cardiac parameters were unaffected. The two studies did show the paradoxical effect of VNS. The contrasting effect should be attributed to the difference in stimulation parameters, mainly the voltage delivered to the nerve. Literature shows that low voltage VNS results in bronchodilatation, while high voltage VNS results in bronchoconstriction. Furthermore, the bronchodilating effect is most likely caused by afferent stimulation, while the side effects in epilepsy are most likely due to efferent stimulation.

Medisch Spectrum Twente (Enschede), Clinical Neurophysiology - M.J.A.M. van Putten, C.C. de Vos (UT: J.A.M. van der Palen, B. ten Haken)

FROM DATA TO CLINICAL RELEVANCE WITH FEETB@CK Akke Bakker

In this thesis I investigated what weight loading parameters provide relevant information for monitoring rehabilitation of hip fracture patients. Dynamic weight loading induces fluid flow in the lacunar-canalicular network of the bones. Osteocytes, the mechanosensory cells, can sense fluid flow shear stress and, depending on the magnitude and frequency of the stress, can initiate bone formation or resorption. Osteocytes desensitize to stimuli, therefore (intercycle) rest needs to be induced to resensitize the osteocytes. The FeetB@ck system can monitor the magnitude, frequency and timing of dynamic weight loading and additional weight loading parameters. It consists of an insole force sensor, an amplifier and a data collector. When weight-loading data is acquired with the FeetB@ck system several processes occur that interfere with the signal. By applying signal conditioning incidences of dynamic weight loading can be detected and analyzed despite of noise, offset and drift. In a repeated measures study, the rehabilitation of 21 hip fracture patients was monitored during their admission to a rehabilitation ward. One day a week the dynamic weight loading was monitored with the FeetB@ck device and the amount of pain and gait and balance scores were determined. Mean age was 80.3 Âą 8.3 (SD) years, 15 females and 6 males were included. Several weight loading parameters showed a linear relationship with rehabilitation: steps, bouts, vertical ground reaction force (vGRF) * steps,

impulse * steps and the maximal and average loading response (p<0.05 for more than 9 subjects). Subjects could be divided in fast (<8 weeks, n=7), intermediate (8-12 weeks, n=8) and long (>12 weeks, n=6) rehabilitation groups. The first 8 weeks of rehabilitation was significantly different (ANOVA, p<0.01) between the groups for steps, bouts, peak vGRF * steps, impulse * steps and the average loading response (figure A). Linear mixed models determined that the activity (steps, bouts, peak vGRF * steps and impulse * steps) of a patient is influenced by the quality of balance and gait. While the loading response is mostly influenced by pain and the quality of gait. Care providers consider the monitoring of these parameters, together with the peak vGRF, relevant. The rehabilitation of patients would be adjusted based on the weight loading measured with the FeetB@ck system. However, insight should be provided in the meaning of the loading response. Concluding, I found that monitoring the activity and the average loading response provides clinical relevant information of rehabilitation of hip fracture patients.

Weight loading parameters during the rehabilitation of hip fracture patients. Patients in the short (green), intermediate (yellow) and long (red) rehabilitation group are displayed.

University Medical Center Utrecht, Traumatology - H.R. Holtslag, T.J. Blokhuis (UT: H.J. Hermens)

THE PROGNOSTIC VALUE OF CONTINUOUS EEG AND NIRS MEASUREMENTS IN PATIENTS AFTER CARDIAC ARREST Thijs Banierink INTRODUCTION Prognostication in patients treated with therapeutic hypothermia (TH) after cardiac arrest (CA) is often difficult. Due to sedation, routine neurological examination is limited to testing brainstem reflexes and reflexes after pain stimuli. Electroencephalography (EEG) is used to assess the brainâ&#x20AC;&#x2122;s electrical activity, while near-infrared spectroscopy (NIRS) can be used to measure regional cerebral oxygen saturation. Continuous EEG patterns 12 hours after resuscitation were previously related to good neurological outcome, while lowvoltage or iso-electric patterns were predictive of poor neurological outcome. The prognostic value of NIRS measurements is not known. We study the prognostic value of continuous EEG and NIRS measurements in patients treated with hypothermia after CA.

MATERIALS AND METHODS Continuous EEG recordings were obtained in 24 patients treated with TH. In 13 of these patients a NIRS measurement was also obtained. The outcome parameter of the NIRS measurement is the regional cerebral oxygen saturation (rSO2). Mean arterial pressure (MAP) and body temperature were also recorded in all patients. The correlation coefficient between the rSO2 and the MAP during the hypothermic, rewarming and normothermic phase are calculated as an index for cerebral autoregulation. The mean EEG power and correlation between the EEG power and the rSO2 were also calculated for those three phases. Neurological outcomes were based on each patientâ&#x20AC;&#x2122;s best achieved Cerebral Performance Category (CPC) score within 6 months after cardiac arrest.

RESULTS The mean rSO2 value during the normothermic phase was significantly different between patients with a poor neurological outcome (CPC 3-5, n=7) and patients with a good neurological outcome (CPC 1-2, n=6). In the other phases no significant difference was found (p-values: 0.38, 0.25 and 0.02 in the hypothermic, rewarming and normothermic phase, respectively). The correlation coefficient between the NIRS value and the MAP was higher (p-values: 0.028, 0.18 and 0.19) in patients with a poor neurological outcome in all phases compared to patients with a good neurological outcome. The EEG power was higher (p-values: 0.024, 0.42 and 0.22) in patients with a good neurological outcome compared to patients with a poor neurological outcome in all phases with significant differences in the hypothermic phase.

The correlation between the EEG and the rSO2 fluctuated around zero in all phases. In addition all parameters showed a large variation in both groups.

CONCLUSION Patients with a poor neurological outcome show higher rSO2 values and a higher correlation between blood pressure and cerebral oxygenation with significant differences in the normothermic phase. The EEG power is larger in patients with a good neurological outcome, while the correlation between EEG and rSO2 shows no difference between the patient groups. The higher NIRS values may be explained by the reduced extraction of oxygen by the injured brain. The increased correlation coefficient in patients with a poor outcome may reflect a reduced cerebral autoregulation. The large variation in parameters, however, severely limits the prognostic value of rSO2 measurements in individual patients.

The mean rSO2 (squares) and standard error (SE) are shown for both groups during hypothermia, rewarming and normothermia. The individual rSO2 values are shown as circles (o). Significant differences between the groups are denoted by an *.

MST - Clinical Neurophysiology: M.J.A.M. van Putten (UT: G. Meinsma, T. Heida, M.C. Cloostermans)

TECHNICAL MEDICINE ROTATION PROJECTS

TRACK ROBOTICS & IMAGING

XperGuide VERSUS CT A comparison between needle 足guidance techniques Wendy Busser

At the department of Intervenional Radiology minimally invasive procedures are performed with use of image guidance. The commonly used imaging techniques are CT and fluoroscopy. Both these techniques have benefits and disadvantages. A new technique, XperGuide, combines the benefits of CT and fluoroscopy: soft tissues are visualized on CT-like images and, with real-time fluoroscopy, the needle path can be followed. This research compares XperGuide and CT for needle guidance towards a target. The comparison is made based on the parameters accuracy, procedure time, radiation dose to the patient and ease of use for both techniques. This comparative study is performed with use of a phantom. Inside the phantom four small spheres are placed. To each of these a needle is guided three times, following different trajectories. The first is an easy, straight down trajectory. The second one is a medium trajectory in which the needle follows an angulated path in the same axial (scanning) plane. The last and most difficult trajectory is double angulated: it follows an angulated path and goes through several axial (scanning) planes. The needle guidance procedures are performed by four radiologists with both CT and XperGuide. In total, 96 needle guidance procedures are performed. The measured and examined parameters are compared for both systems.

statistically significant higher for XperGuide compared to CT. It can also be seen that the dose increases for CT with an increase in difficulty, whereas it is similar for the three trajectories for XperGuide. The outcome of the questionnaire for ease of use shows that XperGuide is considered more useful for needle guidance in comparison to CT. Regarding the ease of use, the opinions are divided: two radiologists refer to XperGuide as the easiest technique, while the other two refer to CT as the easiest technique. The overall conclusion is that XperGuide is preferred over CT for the more difficult, angulated trajectories. This will, however, result in a higher patient radiation dose.

The accuracy is determined by calculating the shortest distance between the needle tip and the target point. The procedure time is measured from the first scan to the last control scan. For the determination of the dose, the given Dose-Length-Product values of the CT scans are converted into an effective dose by a known conversion factor. The Dose-Area-Product values, given by the Xper system, are converted by a self-determined conversion factor. The comparison of the ease of use and usefulness of both systems is performed with use of a questionnaire in which statements are scored. The results of the comparison between XperGuide and CT show that the accuracy achieved with XperGuide is better compared to CT. The hard en medium trajectories result in significant smaller distances for XperGuide procedures. For the easy trajectory, there is no difference. The achieved accuracies for the three trajectories are similar for XperGuide, where for CT the accuracy decreases with an increase in difficulty. Regarding the procedure time, no significant differences are found between CT and XperGuide. An increase in time is found with increasing difficulties. The radiation dose results show that the dose is 40

Radboud University Nijmegen Medical Centre, Radiology - L.J. Schultze Kool (UT: C.H. Slump - Philips: A. Balguid)

VISUALISING TINNITUS WITH fMRI AND EEG Michelle Heijblom

PURPOSE

RESULTS

Tinnitus is the continuous perception of a sound that cannot be heard by others. At present, there is no treatment that can completely suppress the tinnitus perception in a large amount of the tinnitus suffering population. The search for such a treatment is complicated by the fact that the pathophysiology of tinnitus is not completely understood. Neuromodulation is a promising therapy for tinnitus. To further investigate the potential of neuromodulation therapy for tinnitus, more information about the underlying tinnitus network should be obtained. We investigate if and how functional Magnetic Resonance Imaging (fMRI) and electroencephalography (EEG) can be used in this context.

We were able to visualise sound induced activity at the auditory cortices with both fMRI and AEPs. Furthermore, we observed differences between individual tinnitus patients and control subjects. In tinnitus patients, sound induced fMRI activity was decreased for the matching sounds as compared with the non-matching sounds. The N100 peak of the AEPs of matching sounds in tinnitus patients was increased with respect to what could be explained by stimulus characteristics and results in control subjects.

METHODS An fMRI pilot study is performed in 2 tinnitus patients and 5 control subjects. In the EEG part of the study, Auditory Evoked Potential (AEP) measurements and spectral analysis are performed in 4 tinnitus patients and 4 control subjects. The subjects are pair-wise matched according to age and applied stimuli. In both fMRI and EEG, subject specific tinnitus matching and non-matching stimuli are applied.

CONCLUSION Both fMRI and EEG can be used to investigate the tinnitus related network. The combination of both modalities and the use of tinnitus matching and non-matching stimuli give additional information about the type of neural activity that is underlying the tinnitus perception. This study is a first step towards clinical use of neuromodulation therapy for tinnitus.

fMRI activity due to a left stimulus (6000 Hz) in a normal hearing subject. The stimulus causes activity at the contralateral auditory cortex. A=anterior, P=posterior, L=left and R=right.

Medisch Spectrum Twente (Enschede), Clinical Neurophysiology - M. Lenders, C.C. de Vos (UT: M.J.A.M. van Putten, T. Heida, C.H. Slump)

DA VINCI ROBOT Introduction and implementation in clinical practice and comparison with laparoscopic surgery concerning view quality Joyce Bomers

PURPOSE Purpose of this study was to verify that the Da Vinci Surgical System is superior on the facet of view quality compared to conventional laparoscopic surgeries. Research parameters were the number of movements and rotation of the camera during surgery and the main working position and main working area in the screen.

MATERIALS AND METHODS With a 3D motion sensor attached to the camera, the movements of the camera were measured during 8 Da Vinci robot-assisted laparoscopic prostatectomies and 5 conventional laparoscopic prostatectomies. The images of all surgeries were recorded on DVD. All data was analyzed afterwards.

RESULTS The mean horizontal and vertical working position were not significantly different (P=0.833). However, the main working area is significant larger for robot-assisted surgery, which means that more time is spent in the periphery of the image in this type of surgery.

The mean number of camera movements per minute was statistical significant: 10.86 ± 1.90 vs. 4.22 ± 0.80, for laparoscopic surgery and robot-assisted surgery, respectively (P=0.002). The camera movements around the different axes were statistical significantly higher in laparoscopic surgery. No statistical difference was observed in the mean number of degrees rotation 4.52 ± 1.54° for laparoscopic surgery and 4.03 ± 2.04° for robot-assisted surgery, respectively (P=0.724). The percentages of time spent with a rotated image of 5°, 10° or 15° were on the other hand statistically significant higher for robot-assisted surgery.

CONCLUSION The quality of view is better in robot-assisted surgery, because the number of camera movements is twice as low compared to camera movements in laparoscopic surgery. The mean working position and the mean rotation are comparable for both types of surgery. The main working area and the time spent with a rotated camera image during robot-assisted surgery were significantly larger, but there is no evidence that this leads to a worse surgical performance.

The Da Vinci robot. (www.intuitivesurgical.com) 42

Radboud University Nijmegen Medical Centre, Radiology - L.J. Schultze Kool (UT: H.F.J.M. Koopman, M.J.A.M. van Putten, I.A.M.J. Broeders)

QUANTIFICATION METHODS IN DYNAMIC AND SMALL-ANIMAL PET Jonathan Disselhorst

Positron emission tomography (PET) is a nuclear medicine imaging technology that uses specific radionuclides that decay by positron emission. These radionuclides are usually bound to a biologically relevant compound, to visualize certain types of tissue. This can either be based on the presence of a certain substance on the cells (e.g. an antigen), or could be related to certain behavior of tissues, e.g. high glucose consumption. A PET-scan can be performed in two different ways, either statically or dynamically. The distribution of the injected radiopharmaceutical is only shown at one point in time in a static scan, while in a dynamic scan, the distribution is followed over time from the start of injection. In this report several aspects of PET have been studied. First of all, dynamic scans of five patients with head and neck cancer with a hypoxia marker ([F-18]FMISO) have been clustered. During clustering, tissues with similar uptake behavior of the marker are grouped together, with the intention to acquire new information about the location and the uniformity of the tumor. For accurate PET diagnosis, a PET scanner should be completely characterized to fully understand its capabilities and limitations. By optimizing scan protocols, including reconstruction settings, more information can be obtained from one study. Aspects of one particular scanner, the Siemens Inveon small-animal PET scanner, that have been studied are the effect of the type of positron emitter on the

image quality, the resolution throughout the field of view (FOV), the effect of dead time and type of normalization, and the optimal reconstruction settings. For characterization, special phantoms and other activity sources have been used. In life-animal situations, all the gained knowledge can be used. In an animal study where mice with specific tumors were imaged using pre-targeted radiopharmaceuticals, aspects of image quality were tested in a real imaging situation. The tumors of the five patients with head and neck cancer showed only very limited signs of hypoxia. The clustering did not achieve the desired results. In one patient, a cluster at the location of the tumor was found, but this was not related to hypoxia. In all patients, clusters could be noticed with anatomic correlations. The clustering of dynamic FMISO scans was based on a combination of certain other tissue properties such as perfusion, instead of hypoxia. The quality of images from the Inveon depended heavily on the choice of radionuclide, and on the type of reconstruction. Maximum a posteriori (MAP) reconstructions delivered the most uniform resolution in the FOV, and showed the highest recovery of small objects, lowest noise and lowest spill-over-ratioâ&#x20AC;&#x2122;s. The scans with different radionuclides showed the positron range had the largest influence on the image quality, with high ranges leading to lower delectability of small objects. Dead time had a limited effect on the scanners performance up to an activity concentration of about 20 MBq/ml. At higher concentrations, the effect was noticeable. Component based normalization proved to be superior to individual LOR based normalization. The pre-targeted radiopharmaceuticals showed high specific uptake in tumors in mice.

MRI (A), CT (B), PET(C) and clustered dynamic PET images at a cross-section through the tumor (D). The tumor has been indicated by a red arrowhead in the MRI image. There is one cluster that correlates with the tumor location and, to some extent, shape. The salivary glands are also part of this cluster, and indicate a similar uptake behavior. In (D), also the mean time-activity-curves of all the clusters are shown. The tumor displays, together with the salivary glands, a larger uptake than the other tissues, also the blood regions show a different pattern compared to the other tissues. The differences however, are in particular large during the first five minutes of the scan.

Radboud University Nijmegen Medical Centre, Nuclear Medicine - E.P. Visser (UT: C.H. Slump, P.H. Veltink)

QUANTITATIVE NUCLEAR CARDIOLOGY Evaluation of perfusion, function and innervation Linda van der Veen

Myocardial Perfusion Scintigraphy (MPS) with the use of electrocardiography-gated single photon emission computer tomography (SPECT) has evolved in an accurate method for localizing and evaluating the extent of perfusion abnormalities within the myocardium. In the last decade, several automatic methods to quantify global and regional perfusion or function are developed. This evolution of MPS has shifted the emphasis of nuclear cardiology from description of perfusion alone, towards describing the perfusion and its effects on the myocardial function.

Acquisition, processing and evaluation of the MPS studies are complex processes. Although the improvements in postprocessing software increase the diagnostic accuracy, there are still various artifacts and errors that can reduce the accuracy of the parameter estimates. Additionally, the introduction of new quantitative indices is often hampered by the lack of studies explaining the mechanisms behind abnormal parameter values, or by the absence of wellvalidated normal reference values. In a clinical practice, where normal limits are often used to categorize and stage patients, it is important to understand the effects of these factors on the parameter estimates. Therefore, the main research question of this thesis was; what aspects of the MPS-protocol affect the quantitative parameters derived by automated analysis? The evaluated factors include; 1. The effect of adenosine on the myocardial function and the implications of adenosine induced stress on the quantitative parameters, 2. The differences between the frequently used software tools Quantitative Gated SPECT and 4DM-SPECT with respect to MPS quantification, 3. The relation between the popularized Transient Ischemic Dilatation and other functional indices, 4. The effect of the injection-acquisition interval on the image quality and quantitative parameters, and 5. The relation between perfusion, function and innervation determined by MPS or 123I-MIBG scintigraphy.

Representation of a normal MPS acquisitions of the same patient in short axis (upper), vertical long axis (middle) and horizontal long axis (lower) directions. Myocardial border estimations are generated by the 4DM-SPECT (left) and Quantitative Gated SPECT (right) software tools, resulting in very different quantitative parameter estimates.

Leiden University Medical Center, Nuclear Medicine - M.P.M. Stokkel (UT: C.H. Slump, A. de Keijzer)

DYNAMIC PET AND DCE-MRI Measurements and Models Monique van Lier

During this internship dynamic PET and DCE-MRI were acquired and used for pharmacokinetic analysis. This pharmacokinetic analysis was executed using compartment models. Compartment modeling results in tissue specific c parameters. These parameters describe the pharmacokinetics of the CA or tracer. It is of great interest whether these parameters could have a prognostic value for patients. However, before the prognostic value of pharmacokinetic parameters could be analyzed the most optimal method to acquire and analyze dynamic images have to be known. During this internship mice experiments were executed. Preclinical research is of importance to test new treatments that could be benefi cial in humans. The use of these dynamic imaging techniques is relatively new in the department. The aim of the study was to test if it is feasible to acquire and analyze dynamic PET and DCE-MR images and to find the best methodology to do this. A lot of knowledge was obtained about the use of dynamic PET and DCE-MRI in mice. At the start of the study the methodology of acquiring and analyzing the PET and MRI images was unknown. This resulted in a challenging search for the best methodology for both imaging techniques. Some additional test were required to come up with the best methodology to acquire and analyze both dynamic PET and DCE-MRI data. For the CA Gadomer-17, as used in the mice experiment, the T1 relaxivity was determined for the 7 T MR scanner. Therefor this MR-system was 11.580. The knowledge obtained during this experiment in acquiring and analyzing dynamic PET and DCE-MRI scans can be used in future experiments. Another aim of the mice study was to

see if the early effects of anti-angiogenic treatment show changes in pharmacokinetic parameters. Unfortunately, clear differences between the two groups were not seen. Due to the small number of mice used in this experiment, significant differences were not expected. For this reason this experiment has to be considered as a pilot study. In the clinical PLuTARCh study, dynamic PET images were acquired. To obtain pharmacokinetic parameters from dynamic PET images several things are necessary. One of these things is the positioning of a ROI. The aim of the initial analysis of the acquired dynamic PET data from the PLuTARCh study was to determine the pharmacokinetic rate constants. This analysis was preformed for a whole tumor ROI but also for different parts of the tumor, to explore the heterogeneity of these tumors. This preliminary study showed that there is an inhomogeneous pharmacokinetics of FDG in the analyzed tumors. The increased FDG uptake in these patients seems to be caused by an increased K1, or by a decrease in k2. These differences between patients could be of interest in the characterization of tumor specific differences. From a large dynamic FDG PET database the pharmacokinetic parameters were used in a survival analysis. The aim of this study was to investigate if the pharmacokinetic parameters obtained from pharmacokinetic modeling of dynamic FDGPET images have a predictive value for overall survival. This study showed no significant differences between pharmacokinetic parameters and the time to death, based on the pre-treatment dynamic FDG PET scans from patients with tumors from different origins and locations. A significant difference in time to death, however, was seen for above median values for SUV and the number of lesions.

Radboud University Nijmegen Medical Centre, Nuclear Medicine - L.F. de Geus-Oei, E.P. Visser (UT: C.H. Slump, A.M. van Cappellen van Walsum)

DYNAMICAL LIGAMENT BALANCING DURING A TKA BASED ON NAVIGATED ROM ANALYSIS Els Reeuwijk INTRODUCTION

METHOD

Besides infection, instability is one of the leading causes of a failed total knee arthroplasty (TKA). Instability of the knee occurs in patients with osteoarthritis, which also effects the laxity of the ligaments. This is what makes the knee instable, because the original collagen fibres of the ligaments around the knee lost part of the original structure. The current ligament balancing techniques only give information on the ligament imbalance in full extension and 90째 flexion. The actual instability of the knee occurs in the mid-range of the range of motion (ROM) and is thereby not included in the current ligament balancing techniques.

A multi-object wrapping algorithm in MatLab is developed to calculate the ligament length over the whole ROM. This algorithm uses combinations of geometrical entities(cylinders, ellipsoids and spheres) to resemble the bone mesh of the knee. It is a dynamic algorithm as it adapts dependable on the flexion angle of the knee. Based on three different types of measurements (saw bone, cadaver and patient), the constants of the main tensile formula are determined by which the module is optimized. Combined with the variable ligament length, this results in an elastic hysteresis stress-strain curve.

GOAL

RESULTS AND DISCUSSION

The main goal is to develop an intra-operative dynamic ligament balancing module-assisting tool for surgeons that give them an indication if the ligament should be balanced during a TKA. The module should give judgement on the laxity of the four ligaments which contribute the most to the stability of the knee and which can be released during surgery; deep and superficial MCL, LCL and the popliteus tendon. The input values for the module should use parameters from the Vector Vision Knee Unlimited system of BrainLab (BrainLab, Munich, Germany) navigation system. Because the ligaments have viscoelastic properties, the hypothesis is that a normal ligament will show an elastic hysteresis stress-strain curve. Based on these curve judgement can be given if laxity is present.

Based on the saw-bone model the positions of these four ligament insertions are determined, as well as the influence of a ligament release is measured in the stress-strain curves of all four ligaments. Based on the patient measurement we can presume that the hypothesis is correct, while taut ligaments showed a smaller elastic hysteresis diameter and higher tensile forces in comparison with looser or lax ligaments. The cadaver measurements showed a large variability.

CONCLUSION While this module gives information on the stability of the knee over the whole ROM, this is a huge progression in comparison with the current static ligament balancing techniques. Based on promising patient measurements, future research is recommended to prevent post-operative mid-range instability after a TKA in the future.

Graphical presentation of the ligament path along the femoral epicondyle(ellipsoid) and the tibial edge(cylinder). (left) Influence of an actual MCL release on the stress-strain curves of the MCL ligaments in a cadaver experiment, where normal ROM (green) are shown versus the MCL release(red).

University Medical Center Utrecht, Orthopedics - D.B.F. Saris (H.F.J.M. Koopman, N. Verdonschot, A.A. van Apeldoorn)

DOSIMETRY FOR RADIOIMMUNOTHERAPY Karen Zegers

Radioimmunotherapy is an innovative cancer treatment, which delivers cytotoxic radiation to the tumor cells. The aim is to maximize the dose to the tumor, while keeping the dose to healthy organs at an acceptable level. Accurate dosimetric calculations are necessary to estimate the radiation absorbed doses to the tumors and healthy organs, because the absorbed dose will relate to therapeutic efficacy and side effects. At the department of Nuclear Medicine, two phase I clinical studies are performed. In the first study radioimmunotherapy is targeted at the CAIX antigen, presented on the majority of renal cell carcinomas. In the second, pretargeted radioimmunotherapy is used to target CEA-expressing colorectal tumors. For both studies dosimetric calculations are performed to estimate the absorbed doses in organs of interest and tumors. Dosimetry based on planar imaging has been the method of choice for a long time, however adjustments can be made to improve this type of dosimetric calculations. To assess adequate tumor uptake, all therapeutic administrations (177Lu) are preceded by a diagnostic administration (111In). In this thesis a method is proposed to predict the therapeutic absorbed doses based on this diagnostic data. In pretargeted radioimmunotherapy the distribution and clearance of activity is highly different in comparison to radioimmonotherapy (using a radiolabeled antibody), therefore adjustments are proposed to improve planar dosimetry for pretargeted radioimmonotherapy. In addition

patient-specific background weighting factors and organ masses are used to determine the effect on the calculated absorbed dose. Planar dosimetry has several limitations like an inaccuracy in the quantification, superposition of organs and a limited attenuation correction. Therefore 3D-dosimetry, based on single photon emission computed tomography (SPECT), is implemented at the department of Nuclear Medicine. From this thesis project can be concluded that: (i) The absorbed doses in healthy organs is significantly reduced by pretargeting. (ii) Diagnostic data can be used to predict the therapeutic dose after (pretargeted) radioimmunotherapy. (iii) Adjustments should be made to calculate absorbed doses for pretargeted radioimmunotherapy, for example using a bi-exponential fit (with correction for background contribution) for the whole body clearance and a red bone marrow to blood ratio of 1 for the calculation of the bloodbased red bone marrow dose. (iv) The use of patient-specific background weighting factors and organ masses changes the calculated absorbed dose significantly. (v) 3D-dosimetry has significant advantages in the quantification of activity when organs and tumors overlap each other. (vi) Similar activity concentrations are determined with SPECT in comparison to planar scans for organs in the abdomen (without overprojection). (vii) In some cases (for example the PRIT study) 3D-dosimetry is necessary to visualize and quantify the tumor uptake.

Above the CT and below the 177Lu-SPECT 6 days p.i. From left to right a transversal, coronal and sagittal plane. In the CT and SPECT the liver tumor is clearly visualized. 47

Radboud University Nijmegen Medical Centre, Nuclear Medicine - M. Gotthardt, E.P. Visser (UT: C.H. Slump, A.A. van Apeldoorn)

INTRODUCTION OF A NEW ROBOTIC TECHNIQUE FOR MRI-GUIDED TRANSRECTAL PROSTATE BIOPSY Safety and accuracy aspects Martijn Schouten INTRODUCTION The detection rate of magnetic resonance image (MRI)guided biopsies after two or more negative transrectal ultrasound guided (TRUS)-guided biopsy sessions is 59%1, demonstrating the potential role of MRI-guided biopsies. Unfortunately, this procedure is time consuming since needle guide positioning is a precise work. Furthermore, during manipulation of the needle guide the target may have moved. For these reasons an in-house pneumatically actuated MR-compatible robotic technique was developed where needle guide direction can be controlled from inside the control room2. It is thought that this robotic technique will improve procedure time and enhance needle guide positioning. Thus, the purpose of our study was to evaluate the accuracy and speed of a novel pneumatically controlled magnetic field compatible manipulator as an aid to perform magnetic resonance image (MRI)-guided biopsies on patients with cancerous lesions in the prostate.

METHODS A pneumatic controlled manipulator with 5 degrees of freedom constructed of plastic to achieve magnetic field compatibility was developed in-house to guide biopsies under real-time imaging4. The targeting and biopsy accuracy of the new robotic technique and the existing commercially available manual device (Invivo, Schwerin,

Germany) to sample a predefined target were measured. In total, 13 biopsy procedures (8 procedures using the robotic technique) were performed on a 3 Tesla whole body closed bore MR system. A target displacement vector was determined for each needle position by evaluating the shift of anatomical landmarks around the cancerous lesions. This in order to determine distance and direction of target displacement. The time needed for both procedures was recorded to evaluate manipulation and procedure time.

RESULTS Both the robotic and manual techniques demonstrated comparable results regarding mean targeting error (5.7 vs 5.8 mm, respectively) and mean target displacement (6.6 vs 6.0 mm, respectively). The mean biopsy error was larger (6.5 vs 4.4 mm) when using the robotic technique, however not significant. Most of the target displacement was in the direction of the needle trajectory. The mean procedure time was 76 minutes using the robotic technique and 61 minutes with the manual technique. Mean manipulation time to move from target to target was 6 minutes with the robotic technique and 8 minutes with the manual technique. Manipulation time and procedure time were not significant different when comparing the robotic and manual techniques.

CONCLUSION Currently, the robotic technique for transrectal real-time MR-guided prostate biopsies did not outperform the manual technique. Furthermore, this study provided insight into reasons for target motion during a biopsy procedure. Our results suggest that most target displacement is caused by needle insertion.

Radboud University Nijmegen Medical Centre, Interventional Radiology - J.J. F端tterer (UT: S. Misra, A. de Keijzer)

EX VIVO MAGNETIC SENTINEL LYMPH NODE DETECTION IN COLORECTAL CANCER Joost Pouw

INTRODUCTION

METHODS

When metastasis is found in the lymph nodes (LNs) after potential curative resection of colorectal cancer, the patient is at high risk of recurrence, and treated with chemotherapy. However, up to 30% of the patients found to be free of nodal metastasis, develop recurrent disease within 5 years. There are strong indications that this high recurrence rate is explained by the presence of very small metastasis in the LNs (occult metastasis), which remain undetected on conventional histopathological examination. These occult metastases can be detected by applying focused examination techniques to the LNs, but this is too expensive and time consuming to apply to all LNs. Sentinel Lymph Node Mapping (SLNM) is a technique used to select the LNs at highest risk of first containing metastasis.

Ex vivo SLNM with Patent Blue and a magnetic contrast agent (Endorem) was performed in 10 colorectal cancer patients. Three blue SNs were selected per patient. The amount of Endorem present in the SNs was quantified by Vibrating Sample Magnetometry, and the SNs were subjected to focused examination.

Colorectal SLNM is currently performed by injecting a blue dye near the tumor, followed by selection of blue lymph nodes, which first received lymphatic drainage from the tumor area. Disadvantages of the blue dye are that it is very easily transported through the lymphatics, and thus selects too many LNs. It also cannot be quantified and is difficult to detect when the LNs are covered by tissue. To overcome these disadvantages we have tested a contrast agent consisting of magnetic nanoparticles, which is potentially more selective, quantifiable and detectable in depth.

CONCLUSION

RESULTS Presence of Endorem was detected in at least one of the three blue SNs in 9/10 patients. The nodal status of all 9 patients was correctly predicted by the presence of Endorem. Nodes harboring occult metastasis were detected by Endorem in 4/9 patients, whom would have been upstaged based on these findings.

Our results demonstrate that blue SNs containing Endorem accurately predict the nodal status of the patient. This indicates that magnetic SLNM can be accurately performed in colorectal cancer. This study is continued and extended in a PhD-project focusing on magnetic lymph node detection, and introducing newly developed magnetic sensing devices clinically.

Submucosal injection of the magnetic contrast agent

Medisch Spectrum Twente (Enschede), Surgery - J.M. Klaase (UT: B. ten Haken, W. Steenbergen)

MEDIASTINOSCOPY OF LYMPH NODES USING FDG-PET/CT IMAGING Françoise Siepel

AIM Image quality of fluordeoxyglucose positron emission tomography (FDG-PET) strongly depends on reconstruction parameters. For standard whole body (SWB) examinations these settings are usually optimized for the entire patient. However, in the thorax region where the level of attenuation and scatter is relatively low, SWB reconstruction might be suboptimal. Consequently, an impact on detection of FDGpositive mediastinal lymph nodes (MLNs) can be expected which may influence lung cancer staging. The aim of this study was to optimize the reconstruction for MLN detection.

MATERIALS AND METHODS First a phantom study was performed which involved data acquisition of the thorax-shaped NEMA NU 2-2001 image quality phantom on a PET/CT (Biograph 40 TrueV, Siemens). The six spheres (D=10-37 mm) were filled with 69 kBq/mL and the background with 12 kBq/mL FDG. PET images were reconstructed using OSEM2D with CT-based attenuation correction. Reconstruction settings were varied by changing the number of iterations (i=4,6,8), subsets (s=8,14,21) and Gaussian post-smoothing filter (G=3,4,5 mm). Subsequently, in each reconstructed image, the Ratio of Uptake values within each sphere to the Noise level (RUN) was measured. Reconstructions with relatively high RUNs (i.e. RUNs > 1) provide images with low noise levels. Disadvantage of these “smooth” reconstructions is that small spheres may not be detected, as low noise levels are strongly correlated to low spatial image resolution. On the other hand, the risk of reconstructions with RUNs < 1 is that tumor tissue may not be separated from noise. Reconstruction settings were determined which provided an optimal combination of high

uptake values and low noise levels (for small objects RUNs just above 1). These settings were used in OSEM3D reconstruction, with a separately optimized Gaussian filter. Next, PET/CT was performed on 15 consecutive patients

The average SUVs of 22 lymph nodes based on the maximum pixel value of FDG-positive MLNs for the SWB and the selected/optimized PET reconstructions. The error bars represent the standard deviation. with a total of 22 suspected positive MLNs. Images were obtained using SWB reconstruction [i=4,s=8,G=5] and the selected/optimized OSEM2D and 3D reconstructions. MLNs were evaluated by measuring Standardized Uptake Values (SUVs) and by visual ranking of anonymized images by 5 experienced nuclear medicine physicians.

RESULTS Reconstructions with optimal RUNs, i.e. RUNS just above 1, were obtained with settings between [i=8;s=8;G=5] and [i=4;s=21;G=5] (OSEM2D), shown in figure 1, and [i=4;s=14; G=3.8] (OSEM3D). Average RUNs significantly improved by 66% with respect to SWB settings (p<0.001). In the patient analysis SUVs were significantly higher for the optimized reconstructions compared to SWB reconstruction (p<0.001). Average SUVs were 5.96 and 6.99 (OSEM2D), 6.49 (OSEM3D) and 5.46 (SWB) (see figure 2). Visual reading was inconclusive, but not in contradiction to abovementioned results. As an illustration, figure 3 shows 4 FDGPET images of MLN reconstructions with optimized and non-optimized settings.

CONCLUSIONS

RUN based on the mean pixel value in a 3D volume of interest determined for the smallest sphere (10mm) in the NEMA NU 2-2001 phantom (visualized in the upper right-corner) as a function of several OSEM2D reconstruction methods. Three groups of reconstructions can be distinguished based on RUNs: images that are too smooth (RUNs>1), images with optimal RUNs just above 1 and images that are too noisy (RUNs<1). 50

Optimized PET reconstruction parameters were derived for detection of FDG-positive MLNs. The improved quantitative measurements (RUNs) imply enhanced detectability of MLNs. These additional reconstructions may improve the diagnostic value of FDG-PET in the prognosis and treatment of lung cancer.

OSEM2D 4i8s5mm

OSEM2D 6i14s5mm

OSEM3D 4i14s3.8mm

OSEM2D 4i14s5mm

Medisch Spectrum Twente (Enschede), Nuclear Medicine - W. de Bruin, J. van Dalen, E.B. van Duyn, F.H.C. de Jongh (UT: C.H. Slump)

NEEDLE GUIDANCE DEVICES IN THE ANGIO-SUITE Optimization of accuracy, radiation dose and puncture procedure time Maarten Kroes PURPOSE

RESULTS

Real-time fluoroscopy guidance using cone-beam CT (CBCT) overlay with dedicated needle path planning software (Philips Allura Xper FD20) is a promising new interventional technique. Disadvantage of real-time fluoroscopy is the radiation dose the operator receives per procedure. The aim of this study was to improve combined CBCT with real-time fluoroscopy guided puncture procedures using additional guidance devices. Especially to assess the effects on radiation hand dose, fluoroscopy time, procedure time and the accuracy.

Due to limitations in the lasers, it was not possible to use the needle guidance device with built-in lasers in the detector of the C-arm for the phantom study. The lowest fluoroscopy time to reach the target was 31s [15-68] for SimpliCT and the combination SimpliCT-needle holders (all data presented as median[ranges]). Freehand (51s [31-99]) and needle holders alone (SeeStar (67s [40-96]) and Simplify (60s [31138])) were all higher in fluoroscopy time, the Bosboom needle holder needed 48s [19-127]. Using SimpliCT and combination SimpliCT-needle holders resulted also in the lowest operator hand dose: 33μSv [5-82] per procedure. This compared to 275μSv [20-603] for freehand, 63 μSv [12-450] for the Bosboom needle holder, 298μSv [80-875] and 167μSv [43-465] for SeeStar and Simplify, respectively. For both fluoroscopy time and dose, laser guided procedures are significantly lower than the freehand technique (p<0.05). Except for the SeeStar, all measured procedure times are significantly longer for the needle guidance devices in comparison to the freehand technique. Accuracy needle-to-target was ±1mm for all needle devices, except for the Bosboom needle holder (2.7mm).

MATERIALS AND METHODS Due to the absent of needle guidance devices developed for assisting XperGuide procedures, the first part of this study is to develop these needle guidance devices. A total of three needle guidance devices were developed. A needle guidance device based on visualizing the needle trajectory by lasers fixated inside the detector of the C-arm (in collaboration with Philips Healthcare (Best, The Netherlands)). An independent laser guidance system (SimpliCT) developed for CT-guided punctures integrated into the angio-suite and specialized for XperGuide procedures (in collaboration with NeoRad (Oslo, Norway)). And a specialized advanced needle holder (designed by Bosboom Engineering (Nijmegen, The Netherlands)). All three needle guidance devices are designed to use the key feature of XperGuide to their advantage, the known angulation information of the planned needle trajectory. These needle guidance devices together with needle holders developed for other image modalities, the SeeStar (AprioMed; Uppsala, Sweden)and the Simplify (NeoRad; Oslo, Norway), were used in a phantom study to compare the performance with the freehand technique (using no additional devices). Fluoroscopy time, hand dose (using active personal dosimeter (Unfors EDD-30)), procedure time and accuracy were measured for each needle guidance device by four interventional radiologists on a phantom (CIRS) with additional internal targets (size 2.3mm). Each device and combination of devices was used three times by each interventional radiologist, using needle trajectories with the same degree of difficulty.

CONCLUSION Laser guidance, alone or in combination with needle holders, achieves the best results of both reduced fluoroscopy time and operator radiation dose while affording good accuracy. Based on these findings, the laser is used as guidance tool in our clinical practice, especially for difficult puncture procedures with small targets.

SimpliCT designed for CT-guided punctures 51

Radboud University Nijmegen Medical Centre, Radiology - L.J. Schultze Kool, F. de Lange, Y.L. Hoogeveen (UT: C.H. Slump, B. ten Haken - Philips: N. Noordhoek)

COLONOSCOPY ROBOT Design of a user interface Nicole Kuperij

INTRODUCTION

EXPERIMENT

The goal of this research was to improve colonoscopy control, because current control methods are complex, not ergonomic and inefficient. A user interface was designed to provide intuitive control. Control of all four Degrees Of Freedom (DOFs) is provided by two features of the interface: a gripping part and an orientation sensing part. The gripping part allows the user to grab the colonoscope shaft and operate rotation (torque steering) and translation (introduction into the anus) of the colonoscope shaft. The other two DOFs, horizontal and vertical tip movement, are controlled by the orientation sensing part of the interface. This is done by using a module that consists of belts and pulleys to actuate the steering wheels at the control handle of a conventional colonoscope. Colonoscope tip control as such can be compared to a stick that pivots at a hole. A setup was built to provide proof of principle after which an experiment was done to investigate the added value for clinical use.

The control method was tested with a colonoscopy simulator that provided a reproducible environment and quantified output measures. Using 12 inexperienced Technical Medicine students, the control method with the Grip was compared to the conventional control method. Two measurements were taken on different days. The time that it took the subjects to reach the caecum was used as a quality indicator for colonoscopy. On average, the group that used the Grip reached the caecum 38% faster (164 seconds, p = 0.06).

CONCLUSION This result confirms the hypothesis that the Grip can offer more intuitive steering. For the clinic, this can implicate shorter learning curves for colonoscopy and more efficient procedures because single handed colonoscope steering can be achieved. Further research at TM (Utwente) and Demcon (Oldenzaal) will reveal the potential of the Grip in a colonoscopy robot.

Meander Medical Center (Amersfoort) and Department of Control Engineering, University of Twente - I.A.M.J. Broeders, M.P. Schwartz (UT: S. Stramigioli, R. Reilink, A. de Keijzer)

FEASIBILITY OF TUMOR PERFUSION QUANTIFICATION WITH GALLIUM-68-CITRATE PET/CT IMAGING IN LIPOSARCOMA AND RADIOTHERAPY Martijn Hoogenboom

The focus in tumor treatments is shifting from tumor cells to the tumor vasculature. Therefore, interest for quantification of the tumor vasculature is rising. Multiple imaging techniques are in development, such as dynamic contrast enhanced Magnetic Imaging (DCE-MRI) or Computed Tomography (DCE-CT). DCE-MR is laborious, expensive and difficult to quantify due to field in homogeneities. DCE-CT yields a radiation dose for a limited field of view. The aim of this thesis is to quantify the change in tumor vasculature with Ga-68-citrate perfusion PET/CT imaging. Ga-68-citrate perfusion PET/CT imaging is a method for perfusion quantification, using the Ga-68-citrate perfusion tracer and dynamic positron emission tomography. The behavior of Ga-68-citrate in the vascular system reveals the possibility to quantify the blood volume in tumor tissue, and leakage to the extra-vascular space as a parameter for vascular permeability. These parameters might be indicative of the treatment outcome of radiotherapy. Ga-68-citrate perfusion PET/CT imaging is divided into three sections of development. First, the development of a mathematical model to describe the behavior of Ga-68 citrate and the correlation with the blood volume of the tumor and permeability of the vessels. Second, the development of a scan protocol and accurate determination of the concentration Ga-68 in the tumor and vascular system. Third, the development of a protocol for elution and labeling of Ga-68 citrate. Three case studies of liposarcoma patients are described. These patients are treated with preoperative radiotherapy. Multiple perfusion PET/CT scans are made before, during and after radiotherapy, to quantify the vascular response to radiotherapy. This thesis provides evidence that it is possible to determine the vascular response (blood volume and permeability of vessels) to radiotherapy. However, the entire procedure should be standardized as much as possible. A mathematical 2 compartment model is described, using a steady state method. This model gives an estimation of the blood volume and permeability of the vessel in the entire tumor, which can be used to quantify the response to therapy. A scan protocol is created in which a PVE correction step is necessary to determine the actual concentration Ga-68 in the tumor and vascular system. Ga68 is eluted from a Germanium generator, the Germanium breakthrough in the elution is 0.04% and has no influences to the dynamic measurements. 53

Based on the follow up of the three patients, is proven that PET/CT can visualize the vascular response of the tumor due to radiotherapy. Each patients respond differently to the therapy which emphasizes the importance of further development of this technique, with the use of a larger patient group.

Patient 1: Example of dynamic vascular permeability Perfusion â&#x20AC;&#x201C;PET scan with gallium-68-citrate of patient One. Shown are two static images at 3 (left) and 30 (right) minutes of a thirty minute dynamic perfusion PET scan. High increase is shown at the tumor, no activity change is shown at necrotic part of the tumor and small decrease of activity is shown at a artery inside the tumor. A decrease of activity is shown as well in the aorta.

Patient 2: The pet scan on the left and a fused PET/CT image on de right. The large MLS on the back of the patient is homogenous mixed with blood.

Patient 3: This patient showed a shift between the CT and PET images, due to movement of the patient between the scans. With the use of Worldmatch the shift is corrected as good as possible thus the delineation of the tumor is still possible with the anatomic information of the CT.

The Netherlands Cancer Institute (Amsterdam), Nuclear Medicine - W.V. Vogel, M. Sinaasappel (UT: C.H. Slump, A. de Keijzer)

OPTIMIZATION OF THE MRI PROTOCOL FOR IMAGING THE SACRAL PLEXUS AND ITS BRANCHING NERVES Pasquelle van der Jagt INTRODUCTION

CONCLUSION

The pediatric urologist is often confronted with children suffering from neurogenic bladder dysfunctioning, caused by congenital anomalies, e.g. spina bifida. Although medical intervention leads to safe urinary continence and preservation of renal functioning, the exact mechanisms of the disturbed innervation of the bladder in the various syndromes and individuals is not known. The hypothesis is that anatomical variations exist in the sacral plexus and that these variations can lead to the distorted innervation of the bladder in children having neurogenic bladder due to congenital anomalies.

In this research an optimized scanning protocol for imaging the sacral plexus and its branching nerves is presented. TSE and DTI with tractography is the most optimal combination of sequences available, giving insight in the anatomy, architectural fiber organization and microstructural properties of the sacral plexus and its branching nerves. Anatomical variations in the sacral plexus are demonstrated regarding branching of the nerves, thickness of the branching L4 trunk with possible changed participation in tissue innervation, and regarding variations in root ascension. First results of MR imaging of the sacral plexus in a boy with spina bifida are demonstrated. Compared to the healthy volunteers no apparent anatomical anomalies are seen. However, a strong indication exists that at the level of the neural tube defect segments of the nerves that are close to the vertebrae exist where lower or disturbed diffusion is present. Consequently, this indicates a change in microstructural properties in these segments, which gives first handhelds in the etiology of neurogenic bladder dysfunction.

METHODS A healthy volunteer study was set up. 10 healthy adults and a 12-year old boy born with spina bifida at the lumbosacral level L5-S1 underwent MRI on a 3.0T system; a DWI, DTI, MEDIC and TSE sequence were applied. Visibility of the first, second and third generation trajectories of the nerves was assessed. Overall means were compared. Post-processing and analysis of the DTI datasets was done using the MRI diffusion toolbox ExploreDTI, acquiring fiber tractography of the nerves as well as maps of the ADC, FA, AD and RD. Furthermore, the anatomical variations were assessed, regarding contribution and thickness of the L4 trunk and the single, double or plexiform root ascension.

RESULTS Analyses of the visibility scores resulted in the finding that the high resolution TSE sequence visualized the nerves of the sacral plexus best. Furthermore, DTI and tractography of the sacral plexus is feasible and herewith insight can be obtained in the architectural configuration and organization of the fibers. In four cases branches to the pudendal nerve were found. Anatomical variations in the sacral plexus were seen regarding branching of the nerves, thickness of the branching L4 trunk with possible changed participation in tissue innervation, and regarding variations in root ascension. In the case study of the boy born with spina bifida assessment of the nerves revealed no abnormal findings. No neural compression was seen in the DWI images. Fiber tractography of the nerves of the sacral plexus was feasible and described a plausible anatomy and 3D fiber organization. However, it was very difficult to track the fiber segments of L5 to S2 that just arose from the vertebrae.

UMCU/WKZ - Pediatric Urology: P. Dik (UT: B. ten Haken, W. Olthuis)

Feasibility Of Tractography Of The Nerves L4 To S2 Of The Sacral Plexus Is Demonstrated.

PHOTOACOUSTIC DETECTION OF MELANOMA METASTASES IN RESECTED HUMAN LYMPH NODES Diederik Grootendorst The pathological status of the lymphatic system is important for accurate staging of different malignancies, ascertaining prognosis and planning treatment. Excision and histopathological assessment of the first draining node is a frequently used method to assess possible malignant involvement of the lymphatic system. Due to the time required for accurate histopathological assessment results are not directly available to the surgeon and finite sampling of the node could result in some metastases to be missed. Accurate assessment of all nodes obtained during a lymphadenectomy could further improve staging once the disease enters a more progressed state. We studied the applicability of photoacoustic computed tomographic imaging (PAI) as an intraoperative modality for examining the status of resected lymph nodes noninvasively. We validated the potential of applying this

technique for patients suffering from possible melanoma metastases by scanning multiple resected human lymph nodes. We validated the photoacoustic imaging results by comparing a reconstructed slice with histopathological sections throughout the node. Our results suggest that photoacoustics has the potential to develop into an intraoperative imaging method to detect melanoma metastases in sentinel lymph nodes in toto.

(a) Photograph of the resected human lymph node. (b) Photoacoustic slice image in roughly the center of the node using 720 nm excitation, showing a diffuse speckled distribution of high absorption. The right center of the node does not contain these high absorption characteristics. (c) Histopathology (H&E) section of the corresponding slice; the darker regions correspond with melanoma cells and the lighter region in the right center is indicative for a necrotic area. (J. Jose, D.J. Grootendorst, T.W. Vijn, M.W. Wouters, H. Van Boven, T.G. Van Leeuwen, W. Steenbergen, T.J.M. Ruers, S. Manohar, Initial results of imaging melanoma metastasis in resected human lymph nodes using photoacoustic computed tomography, 2011, Image published with permission of JBO)

The Netherlands Cancer Institute (Amsterdam), Surgery - T.J.M. Ruers (UT: S. Manohar, A.A. Poot)

DISCRIMINATION BETWEEN BENIGN AND MALIGNANT TISSUE IN THE HUMAN PROSTATE USING DIFFUSE REFLECTANCE AND FLUORESCENCE SPECTROSCOPY Jarich Spliethoff

In prostate cancer (PCa), both needle biopsy procedures and resection procedures show serious shortcomings and still fail too often, which results in a major impact for the patient. Providing complementary real time information during prostate biopsies and during resection of the prostate by means of optical tools could be of significant additional clinical value in prostate cancer. This thesis evaluates whether an optical spectroscopy system can provide accurate information on tissue diagnosis in the human prostate. Prostatic tissue of 27 excised prostates was measured optically using Diffuse Reflectance Spectroscopy and Fluorescence Spectroscopy. The optical measurements were compared to standard histopathological analysis, as gold standard. In the course of the project we discovered that additional chromophores were needed to fit the tissue measurements with the theoretical model. Carotenoids, a family of natural dyes, appeared to be the most likely candidates. On average, the concentration of the carotenoid Î˛-carotene proved to be higher in tumor and other optical parameters proved to be significantly different in PCa as well. However, the pathology slides and an individual-patient analysis demonstrated that both normal and malignant prostatic tissue is highly inhomogenous. Although it appeared that the method of measurements reduced the resolution of the optical measurement, PCa was discriminated with a sensitivity and specificity of 85% and 91%, respectively, when a combination of DRS and FS was used. Even though not all principles behind the changes in optical parameters are fully understood yet and further research is recommended, we can state that this study demonstrated the feasibility to identify Prostate Carcinoma based on optical properties measured by optical spectroscopy.

The Netherlands Cancer Institute (Amsterdam), Surgery & Philips R&D - H.G. van der Poel (UT: T.J.M. Ruers, A. de Keijzer - Philips: B.H.W. Hendriks)

DIFFERENTIATION OF PROSTATITIS AND PROSTATE CANCER USING DIFFUSION WEIGHTED IMAGING AND MR-GUIDED BIOPSY AT 3T Klaas Nagel PURPOSE

RESULTS

To differentiate between prostatitis and prostate cancer (PCa), based on apparent diffusion coefficients (ADC) values, using magnetic resonance (MR)-guided biopsy specimens as the standard of reference.

In total 116 biopsy specimens were included in our study. The median ADC values of normal prostate tissue, prostatitis, low grade PCa (Gleason grade components 2 or 3) and high grade PCa (Gleason grade components 4 or 5) were 1.22x10-3 mm2/s (SD±0.21), 1.08x10-3 mm2/s (SD±0.18), 0.88x10-3 mm2/s (SD±0.15) and 0.88x10-3 mm2/s (SD±0.13), respectively. The median ADCs of biopsy specimens with prostatitis were significantly higher compared to low and high grade PCa (P<0.001).

MATERIALS AND METHODS MR-guided biopsies were performed in 130 consecutive patients with cancer suspicious regions (CSRs) on multiparametric MR imaging at 3T. The need for informed consent was waived by the Institutional Review Board. During the biopsy procedure, an axial diffusion-weighted sequence was acquired with construction of ADC maps (TR/ TE, 2000/67 ms; section thickness, 4 mm; in-plane resolution, 1.8x1.8 mm and b-values of 0, 100, 500 and 800 s/mm2). Subsequently, a confirmation scan with the needle left in situ was acquired and projected on the ADC map. The corresponding ADC values at the biopsy location were compared with the histopathological outcomes of the biopsy specimens. Linear mixed-model regression analyses were used to test for ADC value differences between the histopathological groups.

CONCLUSION DWI is a non-invasive imaging technique enabling differentiation between prostatitis and PCa using MR-guided biopsy specimens as standard of reference, although its usability in clinical practice is limited.

A 66-year old male (PSA, 21.6 ng/mL) with a cancer suspicious region (CSR) in the peripheral zone. Biopsy revealed a Gleason 3 + 3 prostate cancer. The CSR of the pre biopsy MRI (red circle) (A) is visible on the ADC map, which is calculated from a axial single-shot echo-planar DWI image by using three orthogonal diffusion gradients (TR/TE, 2000/67 ms; b values, 0, 100, 500, 800 s/mm2). Control T2-weigthed TRUE-FISP image (TR/TE, 4.48/2.24 ms) during biopsy in axial and sagittal plane shows the position of the biopsy needle (cyan line) with a sampling core length of 17 mm (green line) (B). After projection of the ADC map on the TRUE-FISP image (C), a ROI was drawn manually with the size and extend of the restricted diffusion region on the ADC map (D).

Radboud University Nijmegen Medical Centre, Interventional Radiology - J.J. Fütterer, F. de Lange (UT: B. ten Haken, H.F.J.M. Koopman)

MRI GUIDED HIFU TREATMENT OF BREAST CANCER WITH ADJUVANT MRI GUIDED RADIOTHERAPY Erik Verburg INTRODUCTION Breast cancer is a life-threatening disease. In the Netherlands only, each year more than 3000 women die due to breast cancer. Breast cancer is being diagnosed more frequently in an early stage (tumor stadium T1 or T2) due to the introduction of breast cancer screening. The standard treatment of early breast cancer is breast-conserving therapy, consisting of breast-conserving surgery and whole breast irradiation. Limitations of this treatment are the cosmetic outcome and healthy tissue has to be removed also to be sure all tumor tissue is taken out. A non-invasive treatment of breast cancer will give a better cosmetic outcome. High-Intensity Focused Ultrasound (HIFU) is a medical procedure using high-intensity focused ultrasound to heat and destroy pathogenic tissue rapidly. It is possible to guide the procedure using images acquired real time with a MRI system and monitor the temperature changes using the same MRI system. Planning the treatment before MRgHIFU treatment is necessary to be sure it is feasible to treat a patient using MRgHIFU. In this study, we discuss the feasibility of improving the treatment logistics of Magnetic Resonance guided HIFU (MRgHIFU) treatment of breast cancer by planning the treatment in advance rather than immediately prior to therapeutically procedures.

STUDY DESIGN To determine the percentage of treatable early detected breast cancers with MRgHIFU the location of the tumor inside the breast and the proximity to critical tissue, like skin and pectoral muscle, are an important factor. We developed an automatic segmentation software tool, which determines the border of the skin and pectoral muscle. To give a representative percentage a database of MR images of 831 early detected breast tumors was used to give an overview of the percentage of treatable breast tumors with knowledge of the limitations of the MRgHIFU system.

During MRgHIFU treatment the breast is imaged to locate the tumor again and to be sure the HIFU treatment heats the right volume. The patient is placed in prone position with the breast located inside cup of the MRgHIFU table. The planning before treatment using diagnostic imaging is only possible when the planning can be transferred to treatment. This transfer can be done using image registration. The feasibility of transfer of planned treatment geometry (target) to treatment was determined in a volunteer study. Finally, the feasibility of target transfer to radiotherapy is determined. The tumor location is also the target for radiotherapy and should therefore be still known after MRgHIFU treatment. This location is known when there is an exact overlap of the planned treatment volume and treated volume. A human tissue mimicking phantom gel, in which temperatures of more than 55oC change the MRI signal strength by reducing the spin-spin relaxation time (T2), was used to determine the overlap between the planning target volume (target volume in radiation therapy) and treatment volume (in MRgHIFU).

RESULTS Ninety percent of the tumors are treatable; assuming that it is possible to treat tumors located more than 2.1 mm from the critical structures. Most tumors are found in the lateral part of the breast, and least frequent, tumors are located in the inferior medial volume of the breast. The target transfer was possible in 1 of the 3 cases when the planning was performed in diagnostic position is registered on treatment images. The phantom study showed that the radius of the volume in which the temperature was above 55oC during treatment is up to 4 cm larger than the radius of the planned volume.

CONCLUSIONS It is possible to improve the treatment logistics of MRgHIFU treatment of breast cancer by planning the treatment in advance. The automatic segmentation software can be used to determine if a tumor is MRgHIFU treatable. The planning can be transferred to the treatment equipment when the breast is properly positioned. The treated volume overlaps the planned treatment volume totally but the size of the planned volume is smaller than the actual treated volume.

Treatment planning, The small green and red circles are 18 feedback cells, The dark green line surrounds the treatment target volume which is filled with the 足treatment cells, the green arrows have a length of 5 mm and represents the difference between tumor volume and treatment target volume. The dark spot is a transverse intersection of the simulated tumor. The large pink area has no meaning in this study.

University Medical Center Utrecht, Image Sciences Institute - H.J.G.D. van den Bongard, K.G.A. Gilhuijs (UT: B. ten Haken, A.A. van Apeldoorn)

PHOTOACOUSTIC ELASTOGRAPHY IN BREAST CANCER DIAGNOSTICS Ellen ten Tije

INTRODUCTION

RESULTS

Photoacoustic mammography is a new technique for breast imaging under clinical research, which is based on the differences in absorption of light between normal and cancerous tissues. Ultrasound is a well-known breast cancer diagnostic imaging technology, for which the option of elastography is a current trend under research. This study investigates if the principles of ultrasound elastography, which is based on imaging the differences in tissue stiffness, can also be applied in and translated to photoacoustic imaging.

The signal shift after compression, which is used to obtain information about the stiffness of the tissue, was observed in the ultrasound experiments and could also be observed in photoacoustic elastography, in some parts of some phantoms. The differences in the signal between the parts of the phantom that did demonstrate a signal shift and the parts that did not are presented and evaluated. The differences in the signals of the ultrasound and photoacoustic measurements contributed to the difference in success of applying the elastography principle to photoacoustic signals and imaging.

METHODS Phantom experiments were done to investigate the possibility of applying elastography in photoacoustic imaging, using phantom materials with mechanical, optical and acoustic properties of breast and breast tumor tissue. A set up was built which was suitable for both ultrasound and photoacoustic phantom compression experiments. The compression applied to the phantom could be monitored precisely and ultrasound and photoacoustic signals were obtained with different compressions.

CONCLUSION

This Figure shows one transversal slice in the middle of the reconstruced photoacoustic volume of the layered chicken phantom with an inclusion of smoked chicken, pre-compression. The horizontal axis represents the axis of compression, with on the left the position of the detector and on the right the position of the light falling on the meat. Negative numbers indicate the protective layer of the detector. The meat starts at Z=0mm. The vertical axis represents the vertical direction of the phantom. The inclusion is visible around between 20 and 30 mm on the Z-axis and from approximately 5 to 15 mm on the y-axis.

This figure shows the same measurement as in Figure 45, with the difference that this is a post-compression measurement. Displacement to the left can be observed as a result of the applied extra compression.

To obtain relative stiffness information about tissue, information from all parts of the tissue are necessary. The method did not succeed in parts of the signal were signal coherency between pre- and post-compression was too low, therefore, improvements in the photoacoustic signal are necessary to provide information about the relative stiffness of tissue with photoacoustic elastography.

Medisch Spectrum Twente (Enschede), Surgery - J.M. Klaase, F.M. van den Engh (UT: S. Manohar, M. Heijblom, A.A. van Apeldoorn)

THE EXPLORATION OF TECHNIQUES FOR LUMEN DETECTION IN HUMAN COLONOSCOPY IMAGES Nanda van der Stap Colonoscopy takes a long time to master, mostly because of the difficult steering mechanism of colonoscopes. By making the steering of colonoscopes easier, a national screening program for colorectal cancer may become more feasible. In this research one option to facilitate colonoscopy is investigated. The research involved is part of the on-going project ‘Teleflex’. The goal was to design and test image processing algorithms which have the potential to steer an endoscope automatically. Earlier, a mechanical interface was developed such that it can be fitted to the proximal end of commonly used flexible endoscopes. The mechanical interface can be controlled by means of a dark region detection algorithm (DRD). In this research, we have tested this algorithm in a more realistic environment. Additionally, four algorithms were explored in order to estimate a Focus of Expansion (FOE), needed to determine the heading direction of the endoscope. They are based on optical flow calculation, which means they use subsequent images to determine the motion of the environment from the camera’s point of view. This information can be used to correct the endoscope in the right direction.

Example of an optical flow result. To improve the results further, the preprocessing can be extended to a large amount. It is expected that targeted preprocessing will have more positive effects with regard to accuracy of estimation and robustness of the steering algorithm, but it should be investigated thoroughly whether this can be done real-time. If a robust and accurate algorithm is developed, animal and human subject testing can be performed. Other directions of future research are the expansion of endoscope functionality and making currently difficult procedures and situations easier. It is not unthinkable that depth estimation can be performed in the bowel using optical flow, as well as a target lock - keeping the endoscope stationary when a difficult procedure is performed.

Clarification of the use of Optical Flow and FOE estimation. The small blue arrows are displacement vectors. OA stands for optical axis. DRD is a robust and accurate technique for lumen detection in the human bowel. We have assessed different optical flow algorithms, of which the Pyramidal Lucas-Kanade algorithm turned out to be the best in terms of accuracy, robustness and computational time. It has a low computational time (0,02645 sec) and a high accuracy (RMS = 5,07%, dropped frames percentage is 0% and mean inlier percentage is 30,7%). In this algorithm, a Shi-Tomasi feature detector was used. The SIFT key point detector also provided good results, but the extra selection step in the SIFT algorithm caused a lot of dropped frames and a dramatic decrease in inlier percentage. 60

Meander Medical Center (Amersfoort) - I.A.M.J. Broeders (UT: F. van der Heijden, S. Misra, R. Reilink, A.A. van Apeldoorn)

DEVELOPMENT OF AN ORAL TONGUE MODEL Maarten van Alphen

This report describes a MSc. thesis on the development of a dynamic model of the human tongue for implementation in a virtual surgery environment. This project is part of the dynamic virtual surgery project to predict functional loss and speech impairment after oral cancer surgery. It aims at the development of a virtual environment of the oral cavity and pharynx. In this environment the optional surgical intervention is performed virtually to define the consequences of surgical intervention on the postoperative functioning. In this thesis project two modeling types (finite element method and principal component analysis) are investigated based on mathematical descriptions and literature data of described tongue models of those categories. Imaging techniques are reviewed to find applications for the project. It is concluded that finite element models are the best option for reaching our goal, since these models facilitate

adjustments in the anatomical geometry and material properties after virtual surgery. A start has been made with a finite element model of the tongue, resulting in a symmetric representation of the tongue. The material properties are adopted from the model developed by Dang and Honda. Although the model is coarse, the observed movements are comparable with literature descriptions. Scar tissue is mimicked by an increased stiffness parameter. When the same muscles are activated, another complementary movement is found comparable with the movement of real tissue. The movement could be explained, based on the location of the elements with increased stiffness. This thesis demonstrates that the finite element model is adequate for developing a virtual environment to perform dynamic virtual surgery in oral cancer finally to predict functional loss and speech impairment.

Differences between movement with and without increased stiffness.

(a) Difference after activation of VER, measured

(b) D ifference after activation of IL, measured at the tongue tip. at the tongue tip.

(d) Difference after activation of IL.

The Netherlands Cancer Institute (Amsterdam), Otolaryngology - A.J.M. Balm, A.M. Kreeft (UT: F. van der Heijden, T. Heida)

WALL SHEAR STRESS CALCULATIONS IN COMPLEX FLOW GEOMETRIES Wouter Potters

Wall shear stress (WSS) describes the tangential force that flowing blood exerts on the vessel wall. WSS directly influences remodeling of the vessel wall, therefore the WSS may serve as an early indicator for vascular diseases such as atherosclerosis. Current methods to calculate WSS have limitations. Therefore, a novel method to calculate timeresolved vectorial wall shear stress (WSS) based on 4D phase contrast MRI (PC-MRI) data was developed in this study. WSS vectors were calculated for each point on the vessel wall using the rate of deformation tensor, the inward normal and the blood viscosity. For each point on the vessel wall, the coordinate system is rotated such that the inward normal aligns with the z-axis. No flow through the vessel wall is assumed, resulting in a simplified rate of deformation tensor. Smoothing splines were fitted to the velocities along the inward normals, while enforcing the no-slip condition, to obtain the shear rates in the rate of deformation tensor. The WSS vector was then calculated and finally the calculated WSS vectors were transformed back to the original coordinate system.

artery (CCA) were used to determine the feasibility of in-vivo WSS calculations and to confirm the findings on resolution dependance of the WSS calculation. The phantom study revealed that increasing resolution resulted in improved approximations of the theoretical WSS. Additionally the standard deviation (SD) of the calculated WSS declined with increasing resolution. The WSS calculation in the in-vivo datasets showed similar increases in mean WSS for increasing resolution. Increased noise variance affected the SD of the calculated WSS, while the mean WSS values remained equal. Rotation of the phantom data did not affect the calculated WSS and segmentation errors had the most profound impact on the calculated WSS values. Compared to previous methods in literature, the newly developed algorithm provides more accurate results. Also the current method is able to calculate WSS on individual points along the vessel wall. Concluding, this work presents a novel method to calculate WSS in-vivo. Software phantom results showed that the calculated WSS converged with increasing resolution, which is in line with earlier research. This effect of resolution was confirmed in in-vivo measurements of the CCA.

The effect of resolution, rotation, segmentation and noise on WSS calculations was assessed using software phantom simulations. In-vivo measurements of the common carotid

Academic Medical Center (Amsterdam), BioMedical Engineering and Physics - C.B.L.M. Majoie, E. van Bavel, A.J. Nederveen, P. van Ooij (UT: C.H. Slump, A.A. van Apeldoorn)

EXPLORATION AND EVALUATION OF QUANTITATIVE MYOCARDIAL PERFUSION MODALITIES Gert Jan Pelgrim PURPOSE

RESULTS

In Europe, every year 2 million people die from coronary artery disease (CAD). The pathogenesis of CAD has been studied extensively and the underlying mechanism is well known. It involves the progression of fatty streaks in the intima of the coronary arteries to fibrous and fatty plaques, which may eventually calcify. For cardiac patients it is important to analyze whether they suffer from the presence hemodynamically significant CAD. Thus, evaluation of coronary artery pathology (morphological information) is needed on the one hand, and on the other hand, assessment of inducible ischemia (functional information) due to coronary narrowing is necessary. Ample modalities are used to analyze myocardial perfusion: SPECT, PET, MRI and possibly CT. All techniques have its advantages and setbacks. Those are described in a review regarding myocardial perfusion imaging. A technique which has potential in combining both functional and morphological information is CT. It has high spatial and temporal resolution, but its value in myocardial perfusion is not validated. Therefore, CT will be compared to another recently introduced myocardial perfusion modality, MRI, regarding visual and quantitative analysis of perfusion.

In qualitative MR analysis, 11 myocardial segments showed a perfusion defect. For semi-quantitative CT analysis, 118 segments, and MR, 138 segments were available. For CT, one patient was excluded due to low perfusion intensity and six segments were outside scanning range. In MRI, one apical slice was not available. CT perfusion upslope was lower in segments with perfusion defect compared to normal (0.146±0.082 versus 0.190±0.063; p<0.05) showing a significant downward trend. MR perfusion upslope showed a comparable downward trend (0.350±0.201 versus 0.421±0.231; p=0.326), however, this trend was not significant.

CONCLUSION Our preliminary results suggest that CT semi-quantitative myocardial perfusion analysis is clinically feasible. CTderived perfusion upslope was lower in segments with perfusion defect compared to normal segments, with MRI as reference standard. This study is a first step towards clinical use of CT perfusion analysis in CAD patients.

METHODS Eight symptomatic patients (5 men; age, 58±10 years) underwent adenosine-mediated myocardial perfusion imaging by second-generation dual-source CT and 1.5T MRI. Qualitative analysis of adenosine perfusion MRI was used as reference standard for presence of myocardial perfusion defects. CT and MR datasets were analyzed semiquantitatively using QMASS software (Medis, Leiden, Netherlands). CT and MR values were normalized for enhancement differences by dividing segment upslope by ‘baseline’ blood pool upslope. Upslope values of both CT and MR were compared in normal and defect perfusion segments. An adjusted AHA-model, with 18 segments (6 apical segments) was used. An impression of a perfusion analysis in a patient with CAD. A dynamic CT perfusion scan shows the contrast build-up in the left-ventricular bloodpool (LVBLOOD) and six myocardial segments (S1-S6). Perfusion in segment S4 is lowered, corresponding to the perfusion defect in the posterior cardiac wall.

University Medical Center Groningen, Radiology - M. Oudkerk, P.M.A. van Ooijen, R. Vliegenthart (UT: B. ten Haken, A.A. van Apeldoorn)

USE OF PROSPECTIVE AND RETROSPECTIVE, PATIENT SPECIFIC, 3D TUMOR AND RED BONE MARROW DOSIMETRY IN NUCLEAR MEDICINE Wietske van der Weg The aim of internal targeted radiotherapy as a treatment for (metastatic) cancer is to ensure an adequate dose to the tumor tissue while avoiding healthy tissue damage. Calculation of the dose on a certain volume is called dosimetry. Three methods for 3D patient-specific dosimetry, namely the S-factor based OLINDA, the dose volume kernel based STRATOS and the Monte Carlo simulations based 3D-RD, were compared in order to determine which method should be preferred under which conditions. Dosimetry on a patient with metastasized thyroid cancer, to be treated with 131I, was performed. This showed that the mean tumor dose did not differ considerably, but a voxel based approach (STRATOS or 3D-RD) has the advantage of showing the dose heterogeneity, and the dose outside the delineated area. The most important finding was that the attenuation correction with ReSPECT was insufficient in the later scans, which lead to a critical underestimation of the tumor dose. By using the body contour of earlier scans for attenuation correction, or a CT scan, this should be avoided in future cases.

images. RBM toxicity was the dose limiting factor of this treatment. Five patients developed a grade 1-2 and two patients a grade 3-4 thrombocytopenia. The toxicity was compared to the RBM doses calculated with the different methods; blood, planar image and LV based. The 3D LV based method showed the best RBM dose â&#x20AC;&#x201C; toxicity relationship. (see figure 1) The mean increase in the tumor to RBM dose ratio was 26% when using 90Y instead of 177Lu. With these dosimetry experiences it seems that dosimetry is not yet robust enough for routine use in the clinic. For research and clinical use a voxel based method is advised because the clinical value of a mean tumor dose (OLINDA result) is limited, and correlation with the response is difficult because of actual dose heterogeneity.

3D dosimetry for the pre-targeted radioimmunotherapy study was the second topic of this research. In this study blood samples, planar and SPECT images after diagnostic 111In and therapeutic 177Lu administration, had already been collected. The attenuation correction with ReSPECT was optimized by using the body contour of the first scan as a reference. Data from 13 patients were used for tumor and (for the first time) red bone marrow (RBM) dosimetry based on 3D-RD. The mean tumor dose was low, ranging from 0.46 â&#x20AC;&#x201C; 3.76 Gy, and lumbar vertebrae (LV) based RBM dose ranged from 0.12 to 0.97 Gy. The RBM dose was also estimated based on the blood samples and the planar Absorbed dose (AD) in the red bone marrow (RBM), calculated with 3DRD, versus the grade thrombocytopenia.

Radboud University Nijmegen Medical Centre, Nuclear Medicine - M. Gotthardt, E.P. Visser (UT: C.H. Slump, A. de Keijzer)

INTRAOPERATIVE MARGIN ASSESSMENT USING DIFFUSE REFLECTANCE SPECTROSCOPY Lotte Lutkenhaus

Surgery is the primary treatment option for most cancer types. However, removing the entire tumor can be challenging due to difficult intraoperative localization, resulting in subtotal tumor excision. This is reflected in positive resection margins that can be histopathologically detected after surgery, and are found to lead to increased local recurrence or decreased overall survival. Intraoperative margin assessment is a tool to reduce the rate of positive margins and re-excisions, but should meet strict requirements to be of added clinical value. These requirements were assessed in a pathology study in liver and breast. It was found that for liver, nodal extrusions on the surface of the tumor dictate a resolution of 1 mm. This is less strict when a sensing depth of approximately 3 mm is chosen, since even missed extrusions will not result in a positive resection margin due to their limited height. In breast, the pathology study indicated a large inhomogeneity of both normal and tumor tissue. Guidelines dictate reexcision of an extensively positive resection edge, which leads to a resolution of 1 mm and a superficial sensing depth (< 1 mm).

Diffuse reflectance spectroscopy (DRS) has the capability to non-invasively discriminate between normal and tumor tissue. It also has the potential to meet the above stated requirements, and can therefore possibly be used for intraoperative margin assessment. The distance between source and detector fiber, i.e. the fiber distance, is the most important system parameter that should be optimized in this. Resolution, sensing depth, sensitivity and specificity all depend on the chosen fiber distance. Margin assessment is characterized by measurements containing both normal and tumor tissue. In phantom experiments and measurements on human liver tissue, the behavior of a DRS probe when a border between two tissue types is measured, was analyzed. It was found that measurements of tumor at different depths can be described with a known equation, resulting in an s-shaped curve which is different for every fiber distance. Fiber distance determines the steepness of the curve, and therefore also resolution and sensing depth. It was concluded that a tool based on DRS has the possibility to intraoperatively assess whether the extent of excision was sufficient.

Positive resection margin in breast cancer, H&E-stained tissue slide. The whitish vacuoles were lipid-filled before processing. The tumor shows a long and narrow extrusions, which reaches the brown-stained resection edge at the location of the arrow.

The Netherlands Cancer Institute (Amsterdam), Surgery & Philips R&D - T.J.M. Ruers (UT: V. Subramaniam, A. de Keijzer - Philips: B.H.W. Hendriks)

AUTOMATIC WHITE MATTER BUNDLE CLASSIFICATION AND EXTRACTION OF ADVANCED SCALAR MEASURES FOR GROUP STUDIES Harm van de Haar

A novel analysis method for the investigation of brain white matter was tested to prove its feasibility and then used to study white matter in autism. By applying a two tensor model to diffusion weighted MR images combined with a recently developed streamline clustering algorithm, two new analysis possibilities arise. First, an automatic white matter labeling algorithm might serve to remove the need of human input for the detection of important white matter structures in diffusion weighted MR images. Second, tract-specific analysis can be performed on the diffusion data, which can

detect crossing white matter bundles and makes white matter analysis more specific. The automatic labeling and tract-specific analysis was performed on several large white matter structures. No significant differences in fractional anisotropy and direction-specific fractional anisotropy between the patient and control group were found. However, the analysis methods have been proven feasible for the use of white matter assessment even though they require several improvements.

Left cingulum

Donders Institute for Brain, Cognition and Behaviour - J.K. Buitelaar, M.P. Zwiers (UT: D.G. Norris, A. de Keijzer)

STROKE DETECTION Detection of early ischemic changes on non-contrast CT scans using an atlas-based segmentation of the ASPECTS areas Floor van Rijn

Early ischemic changes (EICs) due to a decreased blood flow to the brain, are an indication of stroke severity. The detection of EICs, seen as subtle hypodense areas on non contrast computed tomography scans (NCCT), is difficult and time consuming, even for experienced radiologists. Hence, stroke severity and risks remain uncertain. The goal of this study is to develop an automated stroke scoring system based on the widely used Alberta Stroke Program Early CT Score (ASPECTS). Firstly, we generated an atlas-based segmentation (ABS) method of the ASPECTS areas. In order to find an optimal ABS method, we tested the accuracy of the ABS and performed subsequent optimization in a train set of 10 patients. An optimal ABS was obtained with an accuracy of 0.45 mm to 1.8 mm, using rigid and affine transformation, followed by a B-spline transformation with a grid spacing of 10 mm. For B-spline a dilated brain mask was used to select only the voxels inside the skull for registration. Secondly we computed the brain density histograms of all ASPECTS areas. We calculated seven features of brain density shift (BDS) between the density histograms of contralateral ASPECTS areas. For each feature of BDS we computed: 1) the sum of BDS in all affected ASPECTS areas and 2) an auto-ASPECTS (10 minus number of affected ASPECTS areas). Highest correlation of auto-ASPECTS and sum of BDS with clinical outcome assessments was obtained using the (shift needed for maximum overlap of the contralateral density histograms), with a threshold of 2.5 HU for EICs detection.

These optimal settings were validated in a test set of 71 patients. Automated brain densitometry of ASPECTS areas was successful in 70 out of 71 cases. One case needed preprocessing. Bland-Altman analysis showed a mean difference of 0.3 between auto-ASPECTS and consensus ASPECTS reading, with a smaller 95% limits of agreement (-2 to 0.41 (P<0.001), than the interobserver agreement of manual ASPECTS (mean difference of 0.377 P=0.001). The manual ASPECTS showed a statistically significant correlation with NIHSS at baseline and at 7-10 days followup and mRS. Auto-ASPECTS showed slightly lower correlations with clinical outcome assessments, especially for NIHSS at 7-10 days follow-up. Automated densitometry based ASPECTS scoring on NCCT scans by comparing contralateral density histograms is feasible and has the potential to reduce interobserver variability of ASPECTS reading in clinical practice.

Academic Medical Center (Amsterdam), Radiology & Leiden University Medical Center, Division of Image Processing - C.B.L.M. Majoie, H.A. Marquering (UT: C.H. Slump, A. van Cappellen van Walsum - LUMC: M. Staring, B.C. Stoel)

EVALUATION OF FIDUCIAL MARKERS FOR STEREOTACTIC BODY RADIATION THERAPY OF COLORECTAL LIVER METASTASES WITH HELICAL TOMOTHERAPY Quirina de Ruiter

PURPOSE

RESULTS

Stereotactic Body Radiation Therapy (SBRT) has proven to be safe and feasible for treatment of colorectal liver metastases. The main challenges of liver SBRT are (1) respiratory motion of the liver, (2) contrast of the tumor in the liver during treatment, and (3) high radio-sensitivity of the liver. During SBRT, locating the exact coordinates of the tumor during treatment can occur with implanted gold fiducial markers into the liver. Currently, the optimal fiducial marker and effect of the marker during respiration is unknown. In this study, the visibility and accuracy of various fiducial markers for the application in SBRT of colorectal liver metastases on Helical Tomotherapy radiation treatment modality is observed. Breathing dynamics were mimicked with a 4D motion phantom, and fiducial markers were evaluated with Megavoltage Computed Tomography (MVCT) of the Helical Tomotherapy.

Best contrast on MVCT was generated by the â&#x20AC;&#x2DC;gold sphereâ&#x20AC;&#x2122; marker, but this marker generated unacceptable artifacts on kVCT. The gold anchor provided the least artifacts on kVCT but visibility on MVCT was limited. All studied fiducial markers had good agreement between the average geometric position and the observed position on MVCT under the studied conditions. The size and number of the observed artifacts on MVCT were dependent on type of marker and specific dynamic conditions. Artifacts on MVCT improved the marker detectability and helped the observer to determine the center of the markers.

M&M Initially fifteen types of markers were imaged in a static water environment and with MVCT. Poor visible markers on MVCT were eliminated leaving six markers for further evaluation in dynamic conditions. A 4D motion phantom was developed and validated with 4D-CT to perform these measurements. A repetitive motion on the studied markers was applied in a water environment. Peak-to-peak amplitude and frequency was varied to analyze the effect of dynamic conditions on the marker detectability on MVCT of a Helical Tomotherapy system. A conventional 4D kilovoltage CT (kVCT) unit was used as reference. The detectability was quantified by analyzing the contrast of the fiducial markers on the obtained images. Also the artifacts on the images caused by the moving markers were analyzed with respect to the amplitude and frequency of the movements.

CONCLUSION Good detectability of all observed fiducial markers was obtained for the studied dynamical conditions. Good agreement was observed between the geometrical average position of the moving markers with respect to the observed position on MVCT. Artifacts generated by the MVCT-image processing can help in determining the position of the markers. This marker was implanted in three patients, who were eligible for liver SBRT. No toxicity or migration of the markers was observed. The patients were successfully treated with SBRT on Helical Tomotherapy.

RISO - Deventer: K. Muller, A.W.H. Minken, R. Westendorp (UT: C.H. Slump, J.F.J. Engbersen)

SEMIAUTOMATIC STEERING OF THE 足FLEXIBLE ENDOSCOPE Functional 足design and evaluation Esther Rozeboom The conventional flexible colonoscope is a relatively safe and effective diagnostic tool in the examination of the human bowel. Apart from its benefits as a diagnostic instrument, the flexible colonoscope has developed into a multifunctional therapeutic tool. However, the instrument comes with several limitations. Primarily, colonoscopy is a painful procedure. Moreover, poor usability restrains scope intubation, limits visualization, causes long learning trajectories and work related injuries. The future with advanced and complex therapeutic interventions will demand even more of the physician. Prior to this thesis, a robotic system has been developed that provides motorized control of a conventional flexible endoscope. The aim of this thesis was to, first, evaluate the usability of a bimanual robotic setup and second, design and evaluate a single-handed steering module to control this robotic system. An evaluation including 24 novices in a simulated environment showed that the bimanual robotic steering system increases usability of a conventional flexible endoscope. Motorization of the colonoscope particularly improves scope intubation, affiliated with patient discomfort. Additionally, the high user preference for both touchpad and joystick interfaces reflects the appreciation of intuitive user interfaces.

A second study determined which intuitive user interface provides optimal efficiency in tip control with the robotic setup. Fourteen participants navigated the endoscopic tip along dedicated targets. A touchpad and joystick were used in combination with several control algorithms, the conventional steering module was added as a reference. A joystick in combination with double gain - rate control proved superior in reducing both time and tip displacement. These findings, together with feedback from consulted clinicians, led to the design of a proof of principle concept. Usability of this concept was evaluated using a learning curve study of 23 Technical Medicine students. The evaluation showed that the single-handed steering module reduced the workload of a colonoscopy, without affecting efficiency and effectiveness of the procedure. 10 medical endoscopists confirmed the feasibility of our proof of concept in clinical practice. The steering module allows the other hand to manipulate additional instruments which could prove especially beneficial in interventional procedures. A bimanual implementation of the intuitive interface is also considered viable, following the straightforward scope handling and similarities with the conventional system. In conclusion, the single-handed steering module improves usability of the colonoscope and is regarded feasible by clinical endoscopists.

The conventional, bimanual and single-handed steering modules for the flexible colonoscope.

Meander Medical Center (Amersfoort) - I.A.M.J. Broeders (UT: S. Stramigioli - Demcon: M.C.J. Franken, J.G. Ruiter)

REAL TIME INTEGRATION OF MRI AND ELECTRO ANATOMICAL CATHETER MAPPING OF THE LEFT VENTRICLE TO IMPROVE CARDIAC STEM CELL DELIVERY RenĂŠ van Es

BACKGROUND

RESULTS

In cardiac stem cell therapy, the aim is to deliver stem cells to the borderzone of the infarcted area. Currently, delivery efficiency of stem cell injection is low (<10%). The stem cells that get in, need to be at the right location, therefore, the challenge is to improve the injection accuracy. In this study we have developed a novel toolbox to register electro anatomical mapping obtained by the Noga system and anatomy from MRI of the left ventricle. The stem cell injection strategy and guidance can be improved by visualization of these pre-procedural acquired data from MRI during the Noga injection procedure.

The average distance between the Noga acquired points and endocardial surface (MRI) was, in the phantom experiment: 2.88_1.34mm, and in the porcine experiments: 2.97_2.23mm. The software toolbox was found easy to use in real time experiments. Magnetic particles were traced with MRI and histology. No fluorescent beads were found.

METHODS A fast real time usable registration algorithm was developed and programmed in Matlab. Inputs for the registration algorithm are a 3D mesh of the endocardium and a Noga dataset. Registration can start after at least 3 corresponding landmarks are identified in both modalities. A phantom experiment was performed to optimize the workflow. In a porcine experiment, 3 pigs, three months after myocardial infarction, had a MRI and Noga. Registration of MRI and Noga was done to quantify the registration accuracy, and assess the alignment of scar areas determined by Noga and MRI. To determine the injection accuracy superparamagnetic iron oxide particles were injected preMRI and traced using T2 star MR images. In the post-MR Noga procedure the particles served as injection site targets and fluorescent beads were injected subsequently. Injections sites were inspected histologically to determine the injection accuracy.

CONCLUSION Our registration algorithm allows real time registration of the Noga on MRI, and combined visualization with delayed enhancement data during the mapping procedure. The registration accuracy is clinically relevant. Our method creates new opportunities for multimodality assessment of local cardiac physiology, and provides important additional information during stem cell injection procedures.

University Medical Center Utrecht, Cardiology - S.A.J. Chamuleau, F.J. van Slochteren (UT: C.H. Slump, T. Heida)

DIAGNOSIS WITH OPTICAL SPECTROSCOPY DURING IN VIVO HUMAN BREAST PROCEDURES Paulien Stegehuis In breast cancer, the frequency of missed cancers due to inadequate biopsy procedures and the number of necessary repeat procedures, show shortcomings in the biopsy procedure. AutoďŹ&#x201A;uorescence spectroscopy (FS) and diffuse reďŹ&#x201A;ectance spectroscopy (DRS) have been researched extensively as a diagnostic tool for discriminating among normal, malignant, and/or benign breast tissues, showing encouraging results. The structural, physiological and biochemical changes in tissue due to the onset of oncogenesis alter the spectroscopic properties of tissue fluorescence and diffuse reflectance. The aim of this study was to investigate the additional clinical value of real-time measurements of optical tissue characteristics during percutaneous biopsy procedures in breast cancer. DRS was used in a wavelength range of 400-1600 nm and for FS a laser with an excitation wavelength at 377 nm was used. Two studies were performed; first a study in which twistmarkers were placed on measured spots and after that, one in which biopsies were taken on the same place, directly after measurements. Both were performed in the operation room, directly after the patient was induced. 55 Patients with a proven breast tumor or fibroadenoma were included in this study, and total of 110 tissue samples were evaluated by a pathologist, to serve as gold standard. A mathematical fitting algorithm, based on the diffusion theory of Farrel, was used to fit the acquired spectra and to obtain biologically relevant parameters.

In the course of this study, the fitting results were found to deviate from the raw measurement spectra, and two additional chromophores were found to improve the model; cytochrome c oxidase and catalase. Also anesthetics were investigated, but these did not influence the measurement spectra. With the statistical Kruskal-Wallis test and a CART algorithm, the results were analyzed. The contribution of fluorescence spectroscopy turned out to be very small, and the results of the biopsy study were better than those of the twistmarker study. A per patient analysis was performed, revealing that the fat fraction of the total water and fat content was the best discriminator between normal and tumor tissue. Overall, tumor tissue was discriminated from normal tissue with a sensitivity and specificity of 90% and 83% respectively. Although these results indicate that this technique definitely has the potential to be of clinical gain during percutaneous biopsy procedures in breasts, definite statements cannot yet be made.

The Netherlands Cancer Institute (Amsterdam), Surgery & Philips R&D - T.J.M. Ruers (UT: V. Subramaniam, C.H. Slump - Philips: B.H.W. Hendriks)

SPINEGUIDE Development of a MRI-based personalized drill guide for pedicle screws in scoliotic thoracic vertebrae Abel Swaan

ABSTRACT Object. Pedicle screw placement in the scoliotic spine is a demanding procedure due to the dysplastic and rotated vertebrae. Misplacements can cause serious complications. An individualized drill guide could enhance precision and shorten insertion time.

METHODS A MR sequence was developed to discriminate cortex of the vertebrae from surrounding tissues. After segmentation the vertebrae were converted to a 3D model. In this model, the safe route of the screws was determined and a template was designed with two drill guides for K-wires. Six templates where used to test the fit and accuracy on a thoracic cadaver spine. Deviation of the entry point and the vector angle were measured by overlaying a MRI of the drilled holes on the preplanning. Finally the holes were used for insertion of screws that were planned to expand the pedicle and stay close to the superior endplate. The position was assessed on CT-images.

Results. The MRI protocol allowed good discrimination of the cortex for segmentation by hand. The 3D vertebra model was adequate, as the fit of the template on the vertebrae was accurate. The mean deviation of the entry point was 1.55±1.07mm (mean ± SD) and the mean vector angle deviation was 3.60±2.36 degrees. All screws were tight within the pedicles with 1 screw breaching the medial wall and 2 screws breaching the superior endplate.

CONCLUSIONS The potential of a MRI based patient specific template with drill guides for pedicle screws was demonstrated. Although many issues need to be optimized, this drill template concept is promising. Personalized drill guides may fasten and improve the safety of pedicle screw placement in the future.

SpineGuide on a vertebra with preplanned K-wires.

University Medical Center Utrecht, Orthopedics - M.C. Kruyt, D.B.F. Saris (UT: H.F.J.M. Koopman, S. Stramigioli, C.H. Slump)

QUANTITATIVE MEASUREMENTS OF CEREBRAL OXYGENATION WITH MRI Jasper Verbree

Hemodynamic impairment after ischemic stroke often associated with a higher recurrence rate in patients with cerebral artery stenosis. Measuring the oxygenation and oxygen consumption might give more insight in the disease severity of stroke, stenosis and other (patho)physiological situations. We present a method to measure oxygenation in the brain using magnetic resonance susceptibility measurements. The susceptibility is measured with a 3D phase acquisition and has straight forward model assumptions compared to other methods. Moreover, it requires no external calibration.

Mean oxygenation values measured along the sagittal sinus for two subjects were 56±7 and 63±6% and the variation of the individual measurements approximately 20%. Oxygenation values obtained from the healthy volunteers are in the physiological range; however the measurements are not stable along the entire vessel length. These results lack validation with multiple subjects, external quantitative techniques and physiological challenges. The feasibility was not tested on patients due to lack of validation of the oxygenation measurement.

Acquisition parameters, such as flow compensation, orientation, and SENSE were investigated. In addition we attempted to improve the measurement by post-processing, which included co-registration, skull stripping, unwrapping, estimating vessel tilt, and correct field inhomogeneities.

Academic Medical Center (Amsterdam), Radiology - C.B.L.M. Majoie, E. van Bavel, A. Nederveen, D. Heijtel (UT: B. ten Haken)

TUMOR SPECIFIC PHOTOACOUSTIC IMAGING OF LYMPH NODES Niels Langhout

OBJECTIVE

RESULTS

The evaluation of lymph nodes for metastases is essential in many melanoma patients. Conventional nodal staging techniques either lack sensitivity or require multiple days for analysis, impairing intra-operative assessment during sentinel lymph node biopsies or regional lymph node dissections. Photoacoustic imaging (PAI) is a non-invasive technique that has the potential of label-free localization of melanin deposits in lymph nodes. In this study we used near infrared multispectral PAI to selectively visualize melanin deposits in intact human lymph nodes.

Multispectral photoacoustic imaging revealed distinctive spectral responses. Selective visualization of the melanin and blood related signal was possible; ultrasound overlay facilitated anatomical correlation. The penetration depth proved highly dependent on the tissue type with maximum penetration up to 2 cm. The entire nodal volume could be scanned within 20 minutes.

METHODS Lymph nodes obtained from eight melanoma patients with a positive sentinel lymph node were scanned using a Vevo LAZR© imager. For each voxel, the photoacoustic spectrum was compared to a reference spectrum of both blood and melanin. Histological coupes verified the location of melanoma deposits and blood vessels.

CONCLUSION Three dimensional, high-resolution mapping of melanoma deposits in resected human lymph nodes can be performed within 20 minutes. The multispectral approach allowed for discrimination of blood and melanin related PA signals which could result in improved detection specificity. Near infra-red light penetrated deep into the tissue, using the ‘optical window’ of tissue. In the future, this non-invasive, label-free detection method might also allow for in vivo staging limiting extensive dissection.

The Netherlands Cancer Institute (Amsterdam), Surgery - T.J.M. Ruers, D.J. Grootendorst (UT: S. Manohar, H. Zwart)

MRI-GUIDED FOCAL CRYOABLATION OF LOCALIZED PROSTATE CANCER Optimization of treatment monitoring and implementation at 3T Kristian Overduin OBJECTIVES MRI-guided cryoablation has recently emerged as a promising minimally invasive treatment option for localized prostate cancer. It was the aim of this thesis to, first, optimize treatment monitoring during MRI-guided prostate cryoablation procedures and, second, safely implement this procedure at 3T (Tesla) field strength.

METHODS Two studies were conducted. First, fast T1-weighted (T1w) gradient echo (GRE) imaging was assessed in accurately monitoring cryoablations in a phantom experiment. Also, initial results of its clinical use were reported. Second, radiofrequency (RF)-induced heating of interventional cryoneedles under clinically relevant worst-case conditions was determined at field strengths of 1.5T and 3T. Subsequently, MRI safety of these needles at 3T was evaluated.

Moreover, due to improved image quality, reduced scan times and improved patient access, initial indications show an average reduction in total procedure time of approximately 15 minutes (~8%).

CONCLUSION In conclusion, the outcomes of this thesis have shown that, first, fast T1w GRE imaging optimizes treatment monitoring during MRI-guided focal cryoablation of prostate cancer and, second, this procedure has been safely implemented at 3T field strength.

RESULTS In the experiments of the first study, fast T1w GRE imaging was found to provide a temperature related T1-contrast that allows the continuous and precise monitoring of frozen tissue extent with an accuracy < 6 mm. In addition, it enables insight into the temperature gradient in the tissue. Clinical applicability of the technique was demonstrated. In the experiments of the second study, RF-induced heating of interventional cryoneedles at field strengths of 1.5T and 3T, under conditions as used during MRI-guided prostate cancer cryoablation procedures, was found to never exceed 1째C. This can be regarded as negligible. However, precaution needs to be taken when any deviation from the routine circumstances is required. Performing the clinical procedure at 3T was proven technically feasible and safe.

IMPLICATIONS Based on these results, fast T1w GRE imaging has been implemented as the routine sequence for monitoring the freezing process during MRI-guided focal cryoablation of prostate cancer at the RUNMC. After all procedures performed using this monitoring method, no complications involving freeze injury to adjacent critical structures have been reported so far. Further, a guideline to ensure cryoneedle MRI safety at 3T was setup. MRI-guided cryoablation of prostate cancer was then implemented at this field strength. At present, eight patients have been successfully treated at the 3T MRI system. No technical failures or MRI safety related issues occurred.

Fast T1w GRE image during MRI-guided prostate cancer cryoablation at 3T. The hyperintense rim (arrowheads) that surrounds the iceball signal void corresponds to cooled but unfrozen tissue at temperatures between 0-10째C, providing insight into the temperature distribution in the tissue. In addition, in comparison to similar images acquired at 1.5T field strength, both image noise and acquisition time of fast T1w GRE images at 3T is markedly reduced.

Radboud University Nijmegen Medical Centre, Interventional Radiology - J.J. F체tterer, F. de Lange (UT: B. ten Haken, H.F.J.M. Koopman)

IMPLEMENTATION OF A WHOLE BODY SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY PROTOCOL IN CLINICAL PRACTICE Willem Grootjans OBJECTIVE Within this master thesis, the image quality of shortened single photon emission computed tomography (SPECT) acquisitions for the purpose of whole body (WB) imaging is investigated by determining the performance of several state-of-the-art image reconstruction algorithms currently available at our institute.

MATERIALS AND METHODS Phantom experiments are conducted with the National Electrical Manufacturers Association (NEMA) NU2 image quality (IQ) phantom. SPECT acquisitions are obtained with a Symbia TruePoint T16 (Siemens Healthcare, Erlangen, Germany) SPECT/CT scanner. The background compartment of the phantom is filled with either an aqueous solution of pertechnetate (99mTcO4-) [69.3 MBq] or indiumchloride (111InCl3) [25.6 MBq]. The sphere to background contrast ratio is 4:1. SPECT acquisitions are obtained with different image acquisition times and background activity concentrations. Images are reconstructed with filtered back projection (FBP) and iterative ordered subset expectation maximization (OSEM) algorithms implemented in Siemens Syngo and Hermes Hybrid Recon Oncology. In addition several experimental maximum a posteriori (MAP) algorithms implemented in Hermes Hybrid Recon Oncology, including those with a quadratic smoothing prior (SMOOTH), median root prior (MRP), and the anatomical Bowsher prior (AMAP), are evaluated. Analysis of image quality is performed by calculating several NEMA NU2-2007 and custom derived image quality parameters. Furthermore, the performance of these algorithms for reconstructing clinical images (i.e. bone, parathyroid, and somatostatin receptor SPECT) reconstructed with these algorithms is investigated.

RESULTS The 3DOSEM reconstructed images demonstrate considerable improvements in calculated CRC of the six spheres as compared to the images reconstructed with FBP, OSEM and 2DOSEM. However, the background variability is considerably increased in the 3DOSEM reconstructed images. Image quality of low count acquisitions is severely degraded by increases in background variability and the occurÂŹrence of image artifacts and shape distortions of the spheres. Regularization through the inclusion of a priori knowledge during image reconstruction of low count SPECT acquisitions is an interesting approach to suppress specific noise characteristics in these images.

The image characteristics observed in the phantom studies, including irregular appearances of the background and shape distortions, also appear to emerge in clinical images.

CONCLUSION With the current state-of-the-art Symbia TruePoint T16 SPECT/CT scanner and image reconstruction algorithms from Siemens and Hermes, the image quality of low count acquisitions is currently insufficient to implement a WB SPECT imaging protocol in clinical practice under the defined imaging conditions. The emergence of severe image artifacts, distortions, and amplification of background variability, results in severe degradation of image quality.

Images of the NEMA-NU2 image quality phantom through the central axial slice reconstructed with different image reconstruction algorithms. The SPECT images are acquired with a background concentration of 7.1 kBqâ&#x2C6;&#x2122;mL-1 of 99mTcO4and an image acquisition time of 48 minutes. Attenuation correction is performed on the FBP reconstructed image using the Chang multiplicative method, whereas X-ray CT based attenuation correction is performed on the OSEM and MAP reconstructed images. A) Siemens FBP, B) Siemens Flash3D, C) Hermes 3DHOSEM, D) Hermes SMOOTH MAP, E) Hermes MRP MAP, F) Hermes AMAP

Radboud University Nijmegen Medical Centre, Nuclear Medicine - M. Gotthardt, E.P. Visser (UT: C.H. Slump, A.J.A. Winnubst)

FUNCTIONAL CONNECTIVITY IN ADHD PATIENTS A resting state fMRI study Raimon Pruim INTRODUCTION

CONCLUSION

Attention-deficit hyperactivity disorder (ADHD) is a multifactorial heterogeneous disorder with impaired executive and motivational processes. This is confirmed by neuroimaging studies which show differences in frontostriatal-cerebellar brain functioning in ADHD relative to healthy controls. Resting-state fMRI studies have shown to be promising in finding pathologies within neurocircuits associated with ADHD.

Adding group level motion covariates can eliminate motion artifacts observed in resting-state networks. Functional connectivity within the executive control network and to a lesser extent in the right fronto-parietal network is impaired in ADHD patients relative to controls. The use of these results in a clinical context needs further research in which integration with other (imaging) modalities might increase its diagnostic value and lead to novel insights in the neurobiology of ADHD.

MATERIALS & METHODS I employed the data-driven independent component analysis in combination with dual regression and non-parametric permutation testing to test for differences in resting-state networks (default mode, left/right fronto-parietal and executive control networks) between ADHD, ADHD-siblings and controls. Possible effects of age and gender within and between the ADHD and control groups are determined. Differences between controls and subtypes of ADHD (hyperactive, inattentive and combined subtypes) as well as differences across subtypes are also investigated. I analyzed resting-state fMRI data of 170 ADHD patients, 92 ADHDSiblings and 80 Controls. Before proceeding to the ADHDrelated analyses I investigated the possible effect of movement during the scan session and validated various methods for correcting residual motion artifacts at the single-subject and group level.

Main finding of the research: Increased functional connectivity (green) in the executive control network (red/ yellow) in ADHD patients compared to controls

RESULTS Significant differences in functional connectivity in all tested resting-state networks were found between participants that exhibited high vs. low levels of motion during scanning. Accounting for motion by including motion-related covariates at the single-subject level did not eliminate these motion-related differences. In contrast, including motioncovariates at the group-level successfully eliminated the effects of motion. After accounting for motion using the group-level covariates, increased functional connectivity was found in ADHD patients relative to controls. Specifically, connectivity was altered in the anterior cingulate cortex, dorsomedial prefrontal cortex and left medial frontal gyrus within the executive control network and of the right superior frontal gyrus within the right fronto-parietal network. The effects within the executive control network seemed to be more pronounced within patients with combined type ADHD relative to patients with inattentive type.

Donders Institute for Brain, Cognition and Behaviour - J.K. Buitelaar, M.J.J. Mennes (UT: C.F. Beckmann, F. van der Heijden)

EPILEPSY SURGERY, VISUAL FIELD DEFECTS AND DIFFUSION TENSOR IMAGING OF MEYER’S LOOP What can we learn? Omar Hertgers BACKGROUND

RESULTS

Assessment of DTI accuracy is essential for useful addition of DTI in the clinic. A known complication of anterior temporal lobe resection (ATLR) for epilepsy is the disruption of the Meyer’s loop. The direct causal relationship between this white matter pathway, visualized by DTI tractography, and the visual fields, is a potential way for assessing DTI accuracy. Our aim is to identify clinical relevant settings using this relationship.

Including T2 hyper intensities for tract damage assessment after surgery improved the linear correlation with the visual defects as compared to only resection volumes. Both FSL and iPlan underestimated the anterior extent of the Meyers loop in both volume ratios and distance measurements, although iPlan showed more underestimation. The best correlation with the visual field defects was found with the resection sizes.

MATERIALS AND METHODS

CONCLUSIONS

14 patients with therapy resistant epilepsy undergoing ATLR and DTI scanning were included. DTI tracts of Meyer’s loop were obtained using the FDT package of FSL 4.1 and iPlan Cranial of Brainlab. Post-operative Goldmann visual scores were used to quantify visual field defects. Post-operative resection cavities and T2 hyper intensities were segmented. All imaging modalities were co-registered, linearly and nonlinearly, to the anatomical MRI. Tract volumes overlapping the resection cavity and T2 hyper intensities (i.e. resected tract volumes) were correlated to visual field defects. In addition, the distances Meyer’s loop - temporal pole and resection sizes were measured.

Correlating DTI imaging with clinical findings has the potential to provide the surgeon with clinically relevant settings for tractography of Meyer’s loop in epilepsy surgery. Thresholds and settings should be as lax as possible, as both methods underestimate the anterior extent of the Meyer’s loop. In addition, our findings suggest including T2 hyperintensities for the assessment of postoperative white matter damage.

Free University Medical Center (VU Amsterdam), Neurosurgery - P.C. de Witt Hamer, J.C. Baayen (UT: C.H. Slump)

GOLD NANOPARTICLES BASED THERANOSTICS IN INTRA-OPERATIVE IMAGING AND ABLATION OF HER2 OVEREXPRESSING BREAST TUMOR CELLS Thomas Vijn

Breast cancer is one of the leading causes of death in women Overall the incidence of breast cancer is 130 per 100.000 persons per year. The survival rates of breast cancer are positive, with 89.9 % chance of survival for nonmetastatic breast cancer in a period of 5 years. However, for metastatic breast cancer the survival rates can be as low as 23.3 % in 5 years. In breast cancer therapy, breast sparing removal of the tumor and resection margins is the current standard. However, after removal of the tumor and its margins, in 6-13% of the cases the tumor margins were found to be positive. Positive tumor margins were found to lead to a 3 fold higher chance of recurrence in breast cancer. Overall, due to the impact of positive tumor margins on survival rates research is performed regarding intraoperative aid in adequate resection of the breast cancer. In this master thesis, research is performed regarding theranostics by the administration of HER-2 antibody and fluorescent dye coated gold nanoparticles. In 30% of the breast tumors, there is over-expression of the receptor HER2 compared to surrounding breast tissue. After administration, the nanoparticles bind specifically to the tumor site and can be used to visualize the effectiveness of the removal of the tumor and its margins. In case of positive margins status, the margins can be specifically ablated by heating the gold nanoparticles with a laser.

In the first part of this research, the conjugation process of antibodies to gold nanospheres was examined. Secondly, the binding affinity of several HER-2 antibody coated gold nanospheres to high and low level HER-2 expressing tumor cells was tested. Next to that, the ablation of tumor cells with a 532 nm wavelength laser was assessed. Finally, the ablation of tumor cells with a 532 nm laser, after incubation with HER-2 antibody coated gold nanospheres was examined. We were able to produce HER-2 antibody coated gold nanoparticles with a one-step conjugation procedure, which are stable in buffer conditions. Furthermore, we found that for incubation times equal to or lower than one hour, the particles bind specifically to high level HER-2 expressing cells. For longer incubation times, internalization and binding to low level HER-2 expressing tumor cells were found to play an important role in the staining. Moreover, we were unable to produce fluorescent particles that stain the cells adequate enough to be visualized with fluorescence microscopy or intra-operatively. Finally, for short incubation times ablation was unsuccessful, after staining of the cells with un-aggregated particles.

The Netherlands Cancer Institute (Amsterdam), Surgery - T.J.M. Ruers (UT: R. Gill, S. Manohar)

MAGNETIC DETECTION OF THE SENTINEL LYMPH NODE IN PATIENTS WITH BREAST CANCER Maarten Grootendorst PURPOSE

RESULTS

Sentinel Lymph Node Biopsy (SLNB) is performed to determine the nodal status in breast cancer patients. The gold standard for SLNB is the combined technique, consisting of a radioisotope and blue dye injection, followed by intraoperative sentinel lymph node (SLN) identification with a gamma probe and/or visually, and subsequent excision. Planar lymphoscintigraphy or SPECT-CT can be used to determine the number and location of SLNs preoperative. The major drawback of the combined technique is the use of radioisotopes, which exposes patients and medical staff to radiation, presents challenges and limitations for theatre scheduling and is not widely available throughout the world.

SLNB was performed in 32 patients. The detection rate of the magnetic and combined technique was 93.8% (30 of 32) and 90.6% (29 of 32) respectively. The magnetic technique was false-negative in one procedure, hence the concordance rate of the magnetic and combined technique was 92% and 100% respectively. A total of 5 patients participated in the MRI-subprotocol. In four patients iron uptake could be identified, and in 75% (3 of 4) there was correspondence between the number of SLNs on MRI and surgery. Lymphoscintigraphy and SPECT-CT predicted the number of SLNs accurately in 50% (2 of 4) patients. The cost analysis revealed that the current costs of the magnetic technique per person are approximately €100,- higher than the combined technique.

A radiation free alternative for intraoperative SLN detection is the use of Superparamagnetic Iron Oxide (SPIO) tracer in combination with a handheld magnetometer. In addition to the use for intraoperative detection, the SPIO tracer also provides contrast on MRI. This allows preoperative localisation of SLNs and potentially non-invasive diagnosis of nodal metastasis. This thesis evaluated the magnetic technique against the combined technique, both for intraoperative detection and preoperative imaging. The primary aim for intraoperative detection was to demonstrate non-inferiority, the primary aim for preoperative imaging was to determine the feasibility of SPIO enhanced MRI for preoperative localisation of SLNs. A cost analysis was performed to evaluate the applicability of the magnetic technique for routine clinical use.

CONCLUSIONS In the current study design the magnetic technique can be considered non-inferior to the combined technique for intraoperative SLN detection and Sienna+ enhanced MRI is feasible for preoperative localisation. This non-radioactive alternative has therefore great potential for revolutionising current practise, both in developing as well as Western countries.

MATERIALS AND METHODS In the Medisch Spectrum Twente patients scheduled for SLNB were included. In addition to the standard procedure, a SPIO tracer (Sienna+®) was injected. SLNs were identified with a handheld magnetometer (SentiMag®), gamma probe and visually. The primary endpoint was detection rate, the secondary endpoint was concordance rate. Non-inferiority was accepted if the detection rate of the magnetic technique was 92% or higher and if the concordance rate was comparable to the combined technique. Lymphoscintigraphy was performed in all patients. Patients participating in the MRI subprotocol also underwent SPECTCT. The preoperative findings of all three imaging modalities were correlated with the intraoperative findings of the SentiMag and gamma probe. Sienna+ enhanced MRI was considered feasible for preoperative SLN localisation if the number of iron containing SLNs on MRI corresponded with the number of iron containing SLNs removed.

Medisch Spectrum Twente (Enschede), Surgery - J.M. Klaase (UT: B. ten Haken, W. Steenbergen)

TECHNICAL MEDICINE ROTATION PROJECTS

TRACK RECONSTRUCTIVE MEDICINE

BONE GRAFTING AND IMPLANTOLOGY IN MAXILLARY SINUS AUGMENTATION SURGERY Reinoud Klijn In the field of dentistry calcium phosphate ceramics/ cements are promising implant materials that are often applied for bone filling defects. However, compared to the use of allogenic, xenogenic or alloplastic grafting materials in sinus augmentation surgery, autologous bone grafting still have to be considered to be the gold standard. Calcium phosphate (CaP) cements have a high potential as next to their osteoconductivity they exhibit a perfect contact with the surrounding tissue when injected in situ. A disadvantage is the slow resorbability of these materials, thereby causing difficulties with respect to brittle fracture after longer implantation periods and a decreased bone ingrowth. The introduction of macroporosity is one way to make calcium phosphate cement more suitable for tissue engineering purposes as it promotes bone ingrowth and increase bioresorption of the material. The resulting macroporosity should be interconnected and large enough to guide tissue ingrowth, however, should not decrease the clinical performance of the cement with respect to handling properties, setting and mechanical strength. The main goal of this research was to assess the degradation and clinical performance of three different calcium phosphate cement for augmenting the maxillary sinus floor in sheep. A maxillary sinus augmentation study in sheep was described to evaluate the degradation rate of three injectable PLGA/CaP cements and to assess the

possibility of new bone formation. Three injectable CaP cements were used as grafting material in sinus augmentation surgery for a healing period of 12 weeks. Subsequently histology and histomorphometry was performed. A total bone volume of 66% was found using an experimental β-TCP as augmentation material. The use of LMW/CaP cement and HMW/CaP cement resulted preliminary in, respectively 47% and 31% of total bone volume. The use of an experimental β-TCP material and the use of LMW PLGA and HMW PLGA/CaP cement are suitable bone grafting substitutes in maxillary sinus augmentation in sheep. However, compared to HMW PLGA/ CaP cement, experimental β-TCP material and the use of LMW PLGA CaP cement resulted in higher total bone volume.

Radboud University Nijmegen Medical Centre, Oral Surgery - G.J. Meijer, J.W.M. Hoekstra (UT: C.A. van Blitterswijk)

NANO-ENGINEERED MICROCHIPS FOR EXTRAHEPATIC ISLET OF LANGERHANS TRANSPLANTATION A first step towards cell-based therapy in type 1 diabetes? Mijke Buitinga

Background. Islet transplantation has several drawbacks including organ donor shortage, islet loss during transplantation and procedure-related complications. In addition, islet function declines after transplantation into the hepatic portal vein indicating that the liver is a suboptimal transplantation site. Alternative extrahepatic transplantation sites that have easier access and a more beneficial microenvironment could improve transplant outcome and a more efficient use of donor tissue. In the current study we have developed a biodegradable microchip scaffold for transplanting islets extrahepatically and studied the role of islet size within these constructs.

Microthermoforming implies shaping of heated polymer films by three-dimensional stretching. Scaffold topology was assessed by Scanning Electron Microscopy (SEM). To determine its applicability for islet transplantation, small (<130μm) and large (>180μm) human and murine islets were seeded into the scaffold and cultured for 7 days. Control islets were cultured free-floating in ultra-low attachment petri dishes. At day 1 and day 7 a static glucoseinduced insulin secretion test was performed in triplicate for 20 islets to assess islet function. Islet samples were obtained for histological analysis to evaluate islet composition and apoptosis.

Methods. Nano-engineered implantable scaffolds, containing microcavities with diameters of ~160μm and ~400μm, were fabricated from 4000PEOT30PBT70 blockpolymers (PolyactiveTM) using microthermoforming.

Results. SEM-analysis showed well-formed microcavities indicating that 4000PEOT30PBT70 could be used for scaffold fabrication. Because of its thin walls, the constructs remained flexible, but nevertheless, were mechanically very stable providing a protective environment for the islets. Human and murine islets were cultured within the constructs and they retained their natural morphology in the scaffold. There were no indications for islet spreading or outgrowth of islet stromal cells. Insulin secretion index was similar between free-floating islets of small and large size after 7 days of culturing. Insulin secretion rate was preserved in scaffolds. Histological analysis of human islets did not reveal a major difference between free-floating islets and islets cultured in the construct. Almost all large islets (free-floating islets as well as islets cultured in the scaffold) contained a necrotic core after 7 days of culturing. However, there was no significant difference in total amount of cells per surface area for each condition in time. Additionally, the percentage of glucagon and insulin positive cells in relation to the total cell number was not significantly different between small and large islets in the different groups and these percentages did not change in time.

Morphology of human islets assessed by light microscopy at day 1 and day 7 (upper and lower panel) and by histological analysis at day 4 (middle panel). The blue arrows indicate the scaffold. 85

Leiden University Medical Center, Nephrology - E.J.P. de Koning, M.A. Engelse (UT: A.A. van Apeldoorn, C.J.M. Loomans)

ISOLATION OF BREAST CANCER STEM CELLS A promising target for breast cancer therapies Lonneke Griep

INTRODUCTION Breast cancer remains a significant public health concern. Despite advances in early diagnosis and treatment, breast cancer causes more than 400,000 deaths worldwide annually. Breast tumors are heterogeneous and consist of phenotypically diverse cells. The hypothesis is that cancer stem cells (CSC) are pivotal in setting this heterogeneous character. CSCs have enhanced tumorigenicity and selfrenewal potential and are thought to be responsible for the relapse in breast cancer patients. Currently, breast cancer therapy is focused on killing the differentiated tumor cells, leaving the CSCs unharmed. Specific targeting of these CSCs will improve the disease-free-survival of cancer patients. To elucidate the role of CSCs in breast cancer, we identified, isolated, propagated and characterized CSCs from human breast cancer cell lines and human breast tumor tissue.

METHODS Human breast cancer cell lines MCF-7 and MDA-MB 231 were used to set up a flow cytometry protocol to identify and isolate CSCs from human breast tumor tissues. CSCs are defined as cells with the CD326+/CD44+/CD24phenotype. To characterize the isolated CSCs in detail, CSCs

isolated from the MDA-MB 231 cell line were analyzed for the presence of the oestrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2), cytokeratin 5 receptor (Ck5) and vitamin D receptor (VDR).

RESULTS The number of CSCs was <0.5% in human breast tumor tissue (n=3) and <5% in the breast cancer cell lines (n>5). CSCs isolated from the MDA-MB 231 cell line were, in contrast with the MDA-MB 231 cells, positive for ER and VDR. These receptors might form a promising target for therapy in ER negative breast cancer patients.

CONCLUSION The results obtained from this study are a valuable contribution to our ultimate aim: the development of a microfluidic device to isolate CSCs from breast tumors and analyze which drug can specifically target CSCs. The outcome of such experiments can provide the physician with extra information in setting the best therapy regime possible, to increase the disease-free survival and with this the quality of life for breast cancer patients.

Design of a microfluidic device to isolate CSCs from breast tumors and analyze multiple drugs on patient specific CSCs and tumor cells.

Medisch Spectrum Twente (Enschede), Surgery, Center for Mammacare - J.M. Klaase (UT: F. Wolbers, H.F.J.M. Koopman, J.N. Post)

LARGE TUBULAR CONSTRUCTS FOR UROSTOMY TISSUE ENGINEERING Mariëlle Walraven

INTRODUCTION Invasive bladder cancer usually requires radical cystectomy followed by creation of a neobladder or a urostomy (ureteroileo-cutaneous anastomosis). The small intestine is often used to create a urostomy. However, complications occur in 30-80% of the patients and may include infection, urinary stones, urine blockages and metabolic disorders. Tissue engineering may be the technical platform to develop alternatives for urinary diversions and prevent/lower complications. This study focuses on the preparation and in vitro evaluation (static and dynamic culturing) of collagenpolymer based large tubular scaffolds for urological surgery.

METHODS Large tubular scaffolds (Ø 3 cm) were prepared from highly purified bovine type I collagen suspension with and without a commercial available synthetic polymer mesh (Vypro II mesh, Ethicon, Inc., Somerville, NJ, USA) frozen in defined moulds, lyophilized and crosslinked. These constructs were analyzed and characterized by scanning electron microscopy (SEM), standard histology (H&E), immunofluorescent (IF) staining (RCK 103 and type I collagen), TNBS assay (degree of crosslinking), and ultimate tensile strength analysis. Characterized scaffolds were seeded with primary porcine bladder urothelial cells and cultured for 1 week under static or bioreactor conditions (Bose ElectroForce® BioDynamic bioreactor, Eden-Prainie,

MN, USA). The cultured scaffolds were analyzed by SEM, H&E, and IF staining (RCK103 and type I collagen).

RESULTS Two types of large tubular constructs were prepared with distinct macroscopic differences (Fig. 1a-d). SEM and H&E revealed that the tubular scaffolds had a highly porous network. The polymer mesh was localized at the outer region of the tube while the luminal side existed of collagen only. Ultimate tensile strength of the polymer-containing construct was significantly increased in comparison with collagen only: 1.25 ± 0.19 N/mm vs 0.25 ± 0.04 N/mm. In both static and dynamic cultures the urothelial cells were evenly distributed in the lumen of the tubular scaffolds (Fig. 1e and f). Cells in the lumen were positive for RCK103, indicating the epithelial phenotype.

DISCUSSION & CONCLUSIONS In this study we have successfully prepared large tubular constructs consisting of highly purified bovine type I collagen and Vypro II mesh. Previous studies showed that collagen scaffolds displayed excellent biological behavior, but these did not meet the high mechanical demands for surgery. Tensile strength of the developed collagen-polymer scaffold was significantly higher than with collagen only. Histology and SEM analyses revealed that culture under bioreactor conditions supported the homogeneous coverage of urothelial cells on the luminal side of the construct. From both mechanical and cytocompatibility results we conclude that the large tubular collagen-polymer constructs may be a suitable candidate scaffold for urostomy. Overall, this study demonstrates the feasibility to produce constructs applicable for tubular tissue engineering, which may lead to new approaches in (pediatric) urological surgery.

ACKNOWLEDGEMENTS This project was financially supported by the EuroSTEC program (LSHB-CT-2006-037409).

Macroscopical differences between tubular constructs: Collagen with (c, d) and without VYPRO II mesh (a, b). Electron microscopical differences between the static (e) and bioreactor (f) cultured constructs. COL: collagen, COL-VYPRO: collagen with vypro II mesh.

Radboud University Nijmegen Medical Centre, Pediatric Urology - W.F.J. Feitz, P.J. Geutjes (UT: A.A. van Apeldoorn, M.J.A.M. van Putten)

EXPLORATION OF NOVEL STRATEGIES IN VITRO TO IMPROVE ENGRAFTMENT IN HUMAN PANCREATIC ISLET TRANSPLANTS Maaike Roefs Pancreatic islet transplantation is a new treatment option for a select group of patients with type 1 diabetes. In islet transplantation insulin-producing beta-cells are obtained from a donor pancreas and transplanted into the portal vein of the patient. Compared to whole pancreas transplantation it is associated with lower morbidity and mortality, but longterm insulin independency is maintained in a minority of treated patients. Only a small fraction of the transplanted islets successfully engraft, in which lack of vascularization plays a role. It is hypothesized that by transplanting prevascularized islets the engraftment and function will improve, leading to a higher efficacy of islet transplantation. In this study prevascularization of islets in vitro was explored, by testing different matrices and their effect on the islets. In addition, a novel transplantation device was proposed and tested in a newly developed bioreactor. Human pancreatic islets were embedded in several threedimensional matrices and it is shown that embedding in fibrin results in sprout formation. Sprouts occurred already after 1 day in culture and increased in length over time. The islets in the fibrin remained viable and functional.

Two islets embedded in fibrin after 1 day (A and C) and the same islet after 2 days (B and D)in culture (100x, scale bar = 100 Îźm). Sprouting is visible after 1 day in culture, and increased in length and number of branch points after 2 days.

In the developed device, named the periluminal pouch, islets were transplanted into the space between the walls of two concentric prosthetic vascular grafts. This pouch might be implanted into the diabetic patient as an arteriovenous anastomosis according to standard surgical procedures, which will provide an environment with high oxygen tension and nutrient supply. The built bioreactor simulated a physiologic environment to some extent, but a better control of conditions is necessary. Islets embedded in the periluminal pouch appeared to remain functional and viable after 2 days in culture. In conclusion, we consider fibrin the optimal matrix to induce angiogenic sprouting. In vivo studies should confirm the hypothesis prevascularization is beneficial for engraftment of transplanted islets. The bioreactor is useful in testing the proposed periluminal pouch, which showed promising preliminary results.

Left: Average sprout length of islets in fibrin after days in culture. A significant increase in sprout length is seen (n=3). Right: Number of sprouts/branch points measured in islets embedded in fibrin. Number of sprouts appears to remain the same between day 1 and day 2, while the number of second branch points increases (n=2).

Leiden University Medical Center, Nephrology - E.J.P. de Koning, M.A. Engelse (UT: A.A. van Apeldoorn, B. ten Haken)

BREAST CANCER STEM CELLS From conventional analysis towards lab-on-a-chip drug screening Marjanne Ymker

Breast cancer is the most frequent form of cancer in the Netherlands. Although, the prognosis of breast cancer has been improved in the past decades, incidence and recurrence rates remain high. Therapy resistance and recurrence are a major problem in the treatment of breast cancer. The hypothesis that stem cells play an important role in tumour biology has received a lot of attention. These socalled cancer stem cells (CSCs) have the ability for selfrenewal and are pivotal in setting the heterogeneous character of a tumour. Besides influencing the origin and growth of tumours, these CSCs play an important role in developing metastasis. Markers for breast CSCs include CD44 expression, lack of CD24 expression and high aldehyde dehydrogenase 1 (ALDH1) expression. CSCs form mammospheres under non-adherent conditions in vitro. Moreover, the CSCs are resistant for most conventional therapies. Therefore specific targets against the CSCs have to be developed; vitamin D is a promising drug aiming at the CSC. To perform research on the CSCs, the CSCs first have to be identified, isolated and cultured. However, the presence of CSCs in breast tumours as well as breast cancer cell lines is rare. For this reason, it is difficult to select the CSCs. Hence, Lab-on-a-Chip (LOC) devices are very promising.

highest CSC population (7.5%), the percentages of CSCs in MCF-7 cells and mammospheres were low and similar to each other (2.2% and 2.5% respectively). No conclusion can be drawn about the enrichment of CSCs in mammospheres. Furthermore, in the MCF-7 cell line, no overlap between the CD44+/CD24- and ALDH1 phenotypes was shown. Preliminary results of the microfluidic chips showed that all three designs have the potential to trap and culture mammospheres. In future experiments, the expression profile of ER, PR, and VDR in the isolated CSCs need to be analysed. Moreover, more experiments with the microfluidic chips are recommended to develop a functional device for ex vivo drug screening on mammospheres and CSCs. When a functional device is created, steps towards the clinical practice can be made. Tumour samples from an individually patient can be analysed, to set up a personalised therapy regime. Finally, personalised medicine will improve therapy outcome by reducing the side effects of the therapy, preventing metastasis and recurrence of the breast cancer.

This study focuses on the identification, isolation and culture of CSCs in vitro using conventional techniques. Furthermore, microfluidic devices are developed to culture CSCs in the form of mammospheres on chip and to perform drug screening experiments. Human breast cancer cell lines MCF-7 and MDA-MB 231, and mammospheres from MCF-7 cells are used in this study. These cells are characterised for the oestrogen receptor (ER), progesterone receptor (PR) and vitamin D receptor (VDR) with immunocytochemistry. Furthermore, the CSCs are identified with the ALDEFLUOR assay and the combination of the ALDEFLUOR assay with the CD24/CD44 assay, to increase the specificity and validity of the assay. Finally, microfluidic chips are designed to trap mammospheres for culture and drug screening.

Mammospheres trapped in a Lab-on-a-Chip device. Scale bar is 500 Îźm.

The MCF-7 cell line showed high expression of ER and PR, the MDA-MB 231 cell line showed no expression of ER and PR. The MCF-7 cells seem to lose ER and PR when cultured as mammospheres, as their receptor expression is lower. Moreover, this study showed a high expression of VDR in the MCF-7 and MDA-MB 231 cell line, and moderate to high expression in the mammospheres. Based on the ALDEFLUOR assay, MDA-MB 231 cells demonstrated the 89

Medisch Spectrum Twente (Enschede), Surgery & Gynecology - J.M. Klaase, M. Brinkhuis (UT: F. Wolbers, W. Steenbergen)

PRE-CLINICAL MODEL FOR REGULATORY T CELL THERAPY Evidence for the inhibitory effect of ex vivo expanded regulatory T cells on skin inflammation using a humanized SCID mouse model Malou Peppelman BACKGROUND

RESULTS

An increased interest is grown in the protective function and immunological role of regulatory T (Treg) cells to operate through Treg cellular therapy in chronic inflammatory disorders. However, before Treg cellular therapy can be realized for these disorders, it is needed to get more insight in the in vivo behavior of these cells. Therefore, we investigated the effect of ex vivo expanded Treg cells in a humanized skin transplant SCID mouse model.

Ex vivo expanded Treg cells maintained the expression of Treg markers and suppressive capacity in vitro. These expanded Treg cells normalized hu-PBMC induced epidermal marker expression of Keratin 10 (K10) and Keratin 16 (K16) and the influx of hu-CD8 T cells in human skin. A decrease of the absolute number of hu-CD4+ and hu-CD8+ T cells in the peripheral blood and spleen was observed after Treg cell co-infusion. Furthermore, Treg cells inhibited T cell activation and proliferation in vivo in the mouse spleen.

METHODS We isolated and expanded natural occurring CD4+CD25+CD127low human Treg cells from peripheral blood mononuclear cells (PBMC) and examined their phenotype and suppressive capacity in vitro. Using a humanized mouse model, we transplanted 12 mice with human healthy skin followed by an infusion of allogeneic huPBMC with or without Treg cells derived from the same PBMC donor. Skin grafts, spleens and peripheral blood were harvested and analyzed by histology and/or flow cytometry (FCM).

CONCLUSION We showed that under the conditions tested, ex vivo expanded Treg cells reduce but do not fully prevent huPBMC induced skin inflammation in vivo.

Epidermal differentiation, reflected by K10(A) and K16(C) positive epidermal surface area (n=1-3). Representative histological pictures of K10(B) and K16(D) staining (20x magnification) are shown. 1) Human skin graft, control. 2) Human skin graft + hu-PBMC infusion. 3) Human skin graft + hu-PBMC/ Treg cell infusion. 4) Human skin graft + human Treg cell infusion.

Radboud University Nijmegen Medical Centre, Immunology - I. Joosten, H.J.P.M. Koenen, P.C.M. van de Kerkhof (UT: A.A. van Apeldoorn, A. de Keijzer)

MEMBRANE TECHNOLOGY FOR THE SALVAGE OF WOUND BLOOD FROM CARDIAC SURGERY Methods to reinfuse a whole blood concentrate C.M. Platenkamp Cardiac surgery consumes up to 10% of donor blood products to compensate for blood loss during and after surgery. Reinfusion of patient wound blood potentially saves donor blood, but the blood contains many hazardous agents (Figure 1). Current available devices for blood processing successfully remove these hazardous agents and yield erythrocyte concentrates, but discard functional platelet and plasma volumes. The quality of this wound blood can already be improved using smart suction techniques and adapting the choice of anticoagulant. The further processing into functional whole blood volumes requires the application of membranes. In this research we investigated two methods that process lost volumes into a whole blood concentrate with membrane technology. In the first method whole blood was filtrated by commercially available micro- and ultrafiltration membranes. The microfiltration membrane removed ~50% of fat and the ultrafiltration membrane concentrated the blood with good clearance. The effectiveness and haemocompatibility of these membranes were negatively affected by the presence of cells. The second method proposes the integration of these membranes in a centrifuge concept (Figure 2, 3). The feasibility of stacking the commercially available micro- and ultrafiltration membranes was shown in a two-chamber stirred cell. In this configuration ~90% of fat was removed and ~90% of desired plasma proteins was recovered.

Figure 1: A depiction of wanted and unwanted agents from wound blood, differentiated on size. Wanted from the cellular contents are red blood cells (RBC) and platelets (PLT). Unwanted agents from the cellular contents are cell (platelet) aggregates and fat. Wanted from the protein contents are all coagulation factors and albumin. Unwanted agents are all aqueous substances, plasma haemoglobin, vasodilatating agents (TNF-Îą) and fibrinolytic agents (fibrin monomer, FM).

Figure 2: Fat and plasma supernatant is filtrated over a double layer interface: a fat filtration membrane (pre-filter) and ultrafiltration membrane. In theory, the fat is removed in the fat filtration membrane; the plasma continues to interact with the ultrafiltration membrane.

In conclusion, it was possible to select membranes able to process wound blood volumes into functional whole blood concentrates. In the future, this technique enables the reinfusion of functional platelets and plasma volumes from wound blood to the patient, further avoiding the use of donor blood.

Figure 3: A continuous (A) and discontinuous (B) design for the filtration of density-separated blood supernatant. In both cases, a vacuum on the permeate side drives a flux over the membrane. A: In a continuous design a vacuum is exerted in the centre. B: A discontinuous design preferably consists of two or more containers. The blood is centrifuged first. Then a membrane is imposed on the supernatant in a piston-like fashion.

MST - Thorax Surgery: J.G. Grandjean (UT: D. Stamatialis, A.A. van Apeldoorn)

BIOPRINTING OF ORGANIZED ZONAL CARTILAGE CONSTRUCTS Michiel Pot

BACKGROUND

RESULTS

Articular cartilage has limited healing capacity which makes repair of the tissue a great challenge. Regenerative treatments fail to restore the complex zonal organization of native articular cartilage, which in situ provides the tissue with its unique biomechanical properties and is important for proper functioning of the tissue. Cartilage tissue engineering aims to restore articular cartilage, and mimicking the zonal organization of native articular cartilage seems a promising approach to create functional and longlasting implants. Hypothesis: With the encapsulation of zonal chondrocytes in alginate hydrogels it is possible to create zonal layered constructs which mimic the organization of native articular cartilage.

Cartilaginous tissue formation was observed in zonal constructs and their controls with immunohistochemistry and biochemistry. In the constructs no zonal collagen fiber orientation was observed. The zonal markers PRG-4 and clusterin were present in constructs cultured in vitro and were distributed throughout the constructs. PRG-4 and CILP were assessed on in vivo constructs, and PRG-4 showed non-specific staining. Staining for CILP was negative.

METHODS Zonal layered hybrid constructs were printed using a BioScaffolder by alternated deposition of a thermoplastic polymer, polycaprolactone, and alginate hydrogels with encapsulated superficial and deep zone chondrocytes. Constructs were cultured in vitro and implanted subcutaneously in mice for 6 and 10 weeks. Harvested constructs were analyzed for GAGs, collagen fiber orientation, and immunolocalization of collagen type II and the zonal markers proteoglycan 4 (PRG-4), clusterin, cartilage intermediate layer protein (CILP) and cartilage oligomeric protein (COMP).

DISCUSSION Bioprinting of organized zonal hybrid cartilage constructs with zonal chondrocytes is a promising method to mimic the complex zonal organization of native articular cartilage in fiber-reinforced implants. Although no zonal differences were observed in our constructs, this organization might result in improved functional properties and long-term stability of the formed cartilage. Further in vivo studies are needed to confirm this. Moreover, bioprinting can be used to print implants which meet the size of a cartilage defect. Conclusion: By printing organized zonal hybrid constructs with encapsulated zonal chondrocytes in alginate hydrogels we were unable to mimic the organization of native articular cartilage.

KEYWORDS: Cartilage, bioprinting, hybrid construct, zonal chondrocytes, polycaprolactone, alginate

Representation of the printing process for hybrid constructs. The BioScaffolder creates a hybrid construct by alternating printing thermoplastic polymer and multiple (cell-laden) hydrogels.

titel University Medical Center Utrecht, Orthopedics - D.B.F. Saris, J. Malda, W. Schuurman (UT: L. Moroni, A. de Keijzer)

KEEP MOVING FORWARD A new p rosthetic device after (partial) foot amputation Inge Mulder

BACKGROUND

RESULTS

The incidence of foot amputations increased till 1994 in the Netherlands to 3.3/100.000 people. Despite these numbers, only a few basic prosthetic and orthotic devices are available, but all lack functionality to restore ankle and foot mobility. Foot amputees with low available installation height still experience the inconvenience of missing ankle/foot mobility daily. Their low velocity and cosmetically bad walking pattern have much influence on their sound leg and overall functioning. A more functional prosthesis would have great impact on their daily activities.

The self selected and maximum walking speed of the case subject at 0°/5° slope was higher using the new foot (0.36 m/s and 0.53 m/s respectively) comparing to the Low Rider (Otto Bock) (0.31 m/s and 0.31 m/s respectively). Using the new foot, a more symmetrical walking pattern was achieved.

CONCLUSION The case study shows that this new prosthetic foot could be an improvement compared to existing prosthetic feet.

OBJECTIVES The aim of this explorative study was to design and test a unique prosthesis for Syme or Pirogoff amputees, with low installation height which restores ankle and foot mobility.

METHODS The new prosthesis was designed and numerically analyzed on aspects concerning strength and deformation. A prototype was tested in a case study to assess the biomechanical behavior of the new foot. As a reference, 6 Syme/Pirogoff amputees were measured. Additionally, all volunteers filled out a questionnaire to evaluate their prosthetic feet.

University Medical Center Utrecht, Rehabilitation - H.R. Holtslag, L. Beersma (UT: H.F.J.M. Koopman, A. de Keijzer) titel

BUILDING THE BIO-MECHANO-REACTOR Design and development of a new tool for Osteoarthritis research Thijs de Jong

INTRODUCTION

OVERALL PROJECT AIM

Osteoarthritis (OA) is not yet a curable disease, that affects a substantial part of the adult population, and current treatments aim only at symptomatic relief. Several research groups focus on OA, and many powerful tools for OA research have been developed, such as animal models, and in-vitro techniques including bioreactors.

The overall aim of this project is to create a new tool for OA research, and to overcome the challenges in-vivo and invitro experiments present. By combining the advantages of an in-vivo animal model of OA and the controllable in-vitro conditions bioreactors offer, a new type of culture system will be created. This tool will allow for a range of new experiments on the development and possible treatments for OA.

Currently no golden standard exists for animal models of OA, and differences between species and method of OA induction make comparison of studies difficult. Furthermore, in animal models a large ‘black box’ is present from the moment of intervention to the moment of analysis. Although in-vitro bioreactor models allow very precise control over several environmental factors, the conditions created by researchers still are often far from the in-vivo environment wherein the cultured tissue normally thrives.

The proposed model is based on the dog, where the ‘Groove model’ might be used as the method of OA induction. The stifle joint of the dog will be isolated and stripped of the muscular anatomy and synovial membrane, leaving the bone, ligaments, menisci and cartilage untouched. These structures will be cultured as a whole. By leaving the ligamentous anatomy intact, and applying movement and load to the joint, important biomechanical stimuli within the normal range of motion can be applied during the culture.

CURRENT PROJECT AIM AND RESULTS The current project aimed at the design and development of the bioreactor component for the proposed model. A joint isolation protocol was developed and validated. It allows for sterile isolation and preparation of a whole canine stifle joint for culturing, without affecting the proteoglycan metabolism of the cartilage. A prototype bioreactor was created from materials that were specifically chosen for their mechanical and (bio)chemical properties. The created prototype showed feasibility for whole joint culture, but some improvements have to be made before it can be used as a longitudonal culture system.

University Medical Center Utrecht, Rheumatology & Clinical Immunology - F.J.P.G. Lafeber, K. Wiegant, S.C. Mastbergen (UT: H.B.J. Karperien, H.F.J.M. Koopman)

CHONDROGENIC AND HYPERTROPHIC DIFFERENTIATION OF HUMAN MULTIPOTENT STROMAL CELLS IN ALGINATE HYDROGEL CONSTRUCTS Jason Doppenberg

ABSTRACT New approaches in bone tissue engineering are based on the principle of endochondral bone tissue engineering. Multipotent stromal cells (MSCs) can differentiate into the mesenchymal lineages. Chondrogenically differentiated MSCs can become hypertrophic, a crucial step in endochondral bone formation. A promising 3D in vitro culture model for chondrogenesis of MSCs comprises of suspension of single cells in hydrogel beads. To improve chondrogenesis and hypertrophic differentiation, we compared single cell versus pellet encapsulation in alginate beads. We hypothesized that pelleted MSCs differentiate hypertrophically more readily than single cells in alginate beads due to the cellular condensation. Cultures of three different human donors were compared after 21 days of chondrogenic priming and 7 days of culture in hypertrophic or chondrogenic medium. In addition, MSC differentiation was compared in different types of alginate gel. Cell viability and chondrogenic differentiation were assessed after 28 days via Safranin-O and collagen type II stainings and

glycosaminoglycans production was quantified. Hypertrophy, as evidenced through collagen type X immunohistochemistry and mineralization, was observed in all donors. ALP activity, a hypertrophic marker, was found in the supernatant of the culture medium and was most predominant in chondrogenically differentiated samples. Hypertrophic differentiation was most extensive in the youngest donor. These samples showed patches cellular condensation where collagen type X and mineralization were present. Embedded pellets showed more differentiation in this respect. No difference in terms of differentiation or viability could be found between alginate types. This study reveals that alginate encapsulation is a suitable model for hypertrophic differentiation of MSCs in vitro. This design could easily be translatable into an in vivo model of endochondral bone tissue engineering.

KEYWORDS MSC, hypertrophy, alginate, chondrogenic differentiation, pellets, beads

University Medical Center Utrecht, Orthopedics - D.B.F. Saris, D. Gawlitta (UT: L. Moroni)

THE DEVELOPMENT OF A BIO-MECHANO-REACTOR FOR THE CULTURE OF A WHOLE STIFLE JOINT: THE MECHANO-REACTOR Michiel Croes

INTRODUCTION

DISCUSSION AND CONCLUSION

A bio-mechano-reactor is currently being developed for the ex vivo culture of a canine whole stiﬂe joint. The mechanical component involves the application of external loads in the model to provide the torques and compressive forces as present in vivo. The resulting kinematics and joint contact pressures provide physiological spatiotemporal stresses acting on the chondrocytes, hereby allowing prolonged culture of the cartilage component in its native environment.

Together, these ﬁndings show that varying tibial torques, in combination with a cyclic axial load of 35% of the dog’s body weight can result in physiological tibiofemoral kinematics and contact pressures in the used model. In the future, a combination of actuators or tension springs can provide these cyclic loads in the design of a mechanoreactor prototype. With this prototype, the effect of different biomechanical parameters on cartilage biology can be studied.

METHODS AND RESULTS A motion and loading apparatus was specially developed for ex vivo measurements of canine tibiofemoral kinematics and intra-articular contact pressures. In a first experiment, canine stifle joints were moved through flexion (n=6) under combinations of tibial torques and axial forces. The relative rotations of the femur and tibia were measured using a motion capture system. It was found that the internal pathway of motion is not an obligatory effect of the passive joint characteristics, but a result of the applied tibial torque. As such, the motion pathways are hardly influenced by additional axial forces. In a second experiment (n=6), we showed that a torque of 0.03- 0.04 Nm/kg should be applied to the tibia cyclically to simulate quadriceps action during the swing phase of gait. The application of this torque resulted in physiological range-of-motions. Subsequently, static contact pressure measurements were performed in the medial and lateral joint spaces using Fuji pressuresensitive films. The stifles (n=3) were subjected to an axial load corresponding to 35% body weight of the dogs to simulate joint loading during stance, and contact mechanics were evaluated at extension and flexion for increasing medial torques applied to the tibia. We found that the application of a limited medial torque of 0.02 Nm/kg was sufficient to approach physiological contact mechanics. Higher torques resulted in an abnormal medial load split.

KEY WORDS Osteoarthritis, articular cartilage, bioreactor, canine, kinematics, contact pressure

Schematic illustration of an actuator-driven mechano-reactor. A: actuators driving flexion-extension, axial loading, and tibial rotation. B: load-cell for monitoring and control of axial loading. C: regulator. D: PC for monitoring

University Medical Center Utrecht, Rheumatology - F.P.J.G. Lafeber, S.C. Mastbergen (UT: J. Rouwkema, W. Steenbergen)

POROUS MICROWELL SCAFFOLDS FOR EXTRAHEPATIC ISLET OF LANGERHANS TRANSPLANTATION Frank Assen Type 1 diabetes is caused by the autoimmune-mediated destruction of insulin producing pancreatic beta-cells of the islets of Langerhans. For a subgroup of patients, despite good glycaemic control using exogenous insulin, normoglycaemia could not be achieved and patients therefore suffer from secondary complications like retinopathy, neuropathy, nephropathy and cardiovascular disease. Many of these patients have refractory episodes of hypoglycemia and hypoglycemia unawareness and are eligible for an experimental treatment involving the transplantation of islets of Langerhans to replace destructed beta-cells. Clinical results are promising as patients show improved hypoglaemic awareness and can become insulin independent, however due to transplantation site specific effects and the late onset of revascularization, there is a massive islet loss the first days upon transplantation and patients need 2-3 donor pancreata to become insulin independent. To enhance the early islet loss and support long term function of islets, dense microwell scaffolds are previously developed. However these scaffolds are not suitable for upscaled clinical constructs since mass transport through the scaffold is low, and vasculature can

only grow in from one side. Three methods for the fabrication of porous microwell scaffolds are developed: salt leaching which involves the addition of porogens in the scaffold that are washed out leaving a void, ultra-short pulse LASER drilling which involves the use of a pico-second LASER to drill through holes with high precision, and micromolding which involves solvent casting on a microfabricated pillared wafer, perforating the film and creating through holes upon demolding, and are used to fabricate porous microwell scaffolds with through holes of 55±26 μm , 136±25 μm and 72±13 μm respectively. Through holes greatly improves glucose diffusion over previous developed dense microwell scaffolds: porous scaffolds reached equilibrium between 4 and 8 hours, while dense and electrospun scaffolds only reached 9% and 30% of equilibrium after 24 hours. Moreover, these scaffolds support the glucose stimulated insulin secretion of residing islets, allow tubular-like structure to form through the scaffold in an in vitro angiogenesis model, and are therefore expected to be suitable for upscaling towards clinical applications in the future.

Leiden University Medical Center, Nephrology - E.J.P. de Koning (UT: A.A. van Apeldoorn, M. Buitinga, S. Manohar)

PREDICTING AND INTERFERING WITH TREATMENT RESPONSE IN HEAD AND NECK CANCER PATIENTS Else Aalbersberg Head- and neck cancer constitutes 6% of all new cancer cases. Treatment consists of surgery, chemotherapy, and/or radiotherapy. When receiving cisplatin and radiotherapy, only 8% of patients benefit from the addition of cisplatin, while the number of patients with severe side-effects rises up to 89%. Meanwhile the overall survival after chemoradiotherapy is 50%. Currently no tools are available to predict which patients benefit from the addition of cisplatin to therapy or to select for the most optimal treatment.

To find new drug targets, a DUB-inhibitor screen was performed with 329 compounds on five head and neck cancer cell lines. This led to the identification of thirteen hits in which at least 50% inhibition of metabolic activity was observed. These targets and compounds will be investigated further in the hope to develop a novel drug for head and neck tumors. Together these projects aim to improve the treatment of head and neck cancer patients by selecting the right treatment for every individual patient.

This thesis focuses on the development of a chemoresponse assay and the search for novel drug targets for head and neck cancer. Primary tumor cells were cultured from tumor biopsies, first through the production of a single cell suspension and later through a histoculture. Tumor cell viability was assessed by flow cytometry, metabolic activity, and histology. The histoculture is a promising method of primary cell culture and should be further developed.

The Netherlands Cancer Institute (Amsterdam), Head and Neck Surgery - C.L. Zuur (UT: J.R.M. Plass, J. Homminga)

A NOVEL NON-INVASIVE TECHNIQUE FOR THE COLLECTION OF UTERINE IMMUNE CELLS Marja ter Meer INTRODUCTION

CONCLUSION

The human uterus provides a unique environment; it is a mucosal area that should serve as a barrier against pathogens, yet it is also designed to accept and protect a developing fetus during pregnancy. Considering the fact that half of the fetal DNA is foreign to the maternal immune system, this is a remarkable immunological phenomenon. The composition of the immune cell population at the time of embryo implantation is considered to be an important factor for a successful pregnancy. Analysis of uterine tissue would provide valuable information on the receptive status of the uterus and could possibly serve as a biomarker for (un)successful pregnancy. Biopsies are commonly applied to obtain uterine tissue, this is an invasive method though. Through menstruation, uterine cells can be collected noninvasively every menstrual cycle. Therefore menstrual blood is being proposed as an alternative source of uterine cells, possibly eliminating the need for biopsies.

Viable endometrial cells can be collected non-invasively using a silicone menstrual cup during menses. The applied method has shown to be reliable and reproducible, between women and between cycles from the same woman. This method offers a unique opportunity to study the female reproductive tract in a non-invasive manner.

METHODS Flow cytometry was used to study the phenotypical and functional properties of immune cells isolated from menstrual blood. Menstrual blood was collected for a period up to 72 hours using a silicone menstrual cup, peripheral blood was taken for comparison. Expression of various surface markers was studied for NK cells and T cells. Various intracellular cytokine production assays were performed to study the functional capacity of the cells. Ten healthy controls and two kidney transplant recipients were included. Up to 5 menstrual cycles from the same women were studied.

RESULTS The population of mononuclear cells isolated from menstrual blood in the first 36 hours of menses is distinctly different from cells isolated from peripheral blood. NK cells isolated from peripheral blood were predominantly CD56brightCD16and showed higher expression of CD103, CD69 and lower expression of CD57 compared to peripheral blood, where NK cells were mostly CD56dimCD16+. T cells isolated from menstrual blood expressed higher levels of CD103, CD69, CXCR4 and showed lower expression of CXCR3 compared to peripheral blood. Both NK cells and T cells were functional and capable of proliferation, as determined by antigen specific intracellular cytokine production assays and CFSE staining.

Gating strategy: showing representative examples of CD45+ immune cells (A) peripheral blood (B) menstrual blood showing high granulocyte content and a relatively small lymphocyte population compared to peripheral blood

Radboud University Nijmegen Medical Centre, Immunology - H.W. van Hamersvelt, I. Joosten, R.G. van der Molen, (UT: J.R.M. Plass, J. Homminga)

DYNAMICS OF RECEPTORS OF THE HER FAMILY Anno Saris

Despite huge efforts in the research field, cancer is still the leading cause of death in the Netherlands. It is responsible for 30% of all deaths in the Netherlands. Cancer is a multifactorial disease which make it difficult or impossible to point out the cause of the disease in one single patient. Cancer, however, is (almost) always initiated by mutations in genes involved in the regulation of cellular processes like, for example, cell proliferation or angiogenesis. A receptor family that is frequently overexpressed in a wide array of cancers is the human epidermal growth factor recptor (HER) family. This receptor family is composed of four members, EGFR (or HER1), HER2, HER3 and HER4. In recent years several targeted drugs have been developed against members of this family. These drugs inhibit intracellular signaling effectively in-vitro but their in-vivo anti-tumor is limited. It is hypothesized that cells might use multiple mechanism to overcome inhibition. These mechanism then lead to altered dynamics causing prolonged intracellular signaling, overexpression or overactivation of other family members and altered endocytosis or receptor sorting. The aim of this study was to determine the dynamics of receptors of the HER family with and without treatment with targeted drugs against these receptors.

CONCLUSION Unstimulated EGFR and HER2 internalization was similar and both receptors re-appeared during incubation at 37Ë&#x161;C. HER3 had highest basal turnover rates and was upregulated after all treatments. HER3 internalization increased after all treatments apart from lapatinib or lapatinib combined with erlotinib. Tested tumor cells increased HER3 SE following erlotinib, lapatinib, cetuximab and trastuzumab exposure. This implies that HER3 is involved in overcoming inhibition of EGFR or HER2.

METHODS FaDu (EGFR and HER3 overexpressing head and neck squamous cell carcinoma), H441 (EGFR and HER3 overexpressing non-small cell lung cancer) and SKBR3 (HER2 and HER3 overexpressing breast cancer) tumor cell lines were treated with tyrosine kinase inhibitors (TKIs) erlotinib against EGFR and lapatinib against EGFR and HER2 and monoclonal antibodies (mAbs) cetuximab against EGFR and trastuzumab against HER2. Surface expression before incubation (SE), non-internalized surface expression after incubation (NI) and the re-appeared expression after incubation (RA) were determined using flow cytometry.

RESULTS Without therapy, EGFR and HER2 internalization was 2-9% after 1 hour further increasing up to 17-20% after 4 hours. HER3 showed 67-85% internalization during the first hour of incubation. Treatment with erlotinib upregulated HER2 and HER3 SE with increased HER3 internalization. Lapatinib upregulated HER2 and HER3 while their internalization decreased. Cetuximab and trastuzumab treatment resulted in HER3 upregulation and increased HER3 internalization while RA decreased. Combined erlotinib and lapatinib treatment decreased HER3 internalization. Combining lapatinib and trastuzumab decreased HER2 dynamics.

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University Medical Center Groningen, Oncology - E.G.E. de Vries, A.G.T. Terwisscha van Scheltinga (UT: W. Steenbergen, J. Herek, C. Otto)

DEVELOPMENT OF SHORT TERM PRIMARY TUMOR CULTURES OF MALIGNANT PLEURAL MESOTHELIOMA CELLS FOR SCREENING AND DEVELOPMENT OF NEW THERAPEUTIC COMPOUNDS Laurel Schunselaar Malignant pleural mesothelioma (MPM) is a relative rare and aggressive disease. MPM incidence is increasing over the last decade, and expected to peak between 2010 and 2020. The standard of care chemotherapy for MPM is cisplatin wit pemetrexed. This therapy is based on results of randomized trials in large cohorts. However, response for a single patient cannot be adequately predicted from these trials. For patients who do not respond to the treatment, the disadvantages of toxicity outweigh the benefits. Personalized therapy, pursued with chemosensitivity testing, can possibly predict response for a single patient. The aim of this study was to develop a short term primary tumor culture model of MPM, which should be suitable for individual chemosensitivity testing. This study showed it is feasible to culture primary MPM cells from pleural fluid and biopsies. Experiments to optimize the culture conditions demonstrated cells could best be cultured under low oxygen conditions.

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Characterization of the primary tumor cultures is very important for the chemosensitivity assay. Cytospins stained with Giemsa were used to identify mesothelial cells. Morphological it is difficult to distinguish reactive mesothelial cells from malignant mesothelial cells in pleural fluid. For this purpose, immunohistochemical markers such as EMA, desmin and ki-67 have been described, but sensitivity and specificity of these markers are generally low. Ki-67 expression in our cultures was 32%, which suggest that the cultured cells are malignant cells. Staining with the immunohistochemistry marker CK 5/6 showed cells retain their epithelial phenotype. Performing a chemosensitivity assay on primary tumor cells was feasible. All cultures were resistant for the standard of care chemotherapy cisplatin with pemetrexed, however sensitive for the combination oxaliplatin with gemcitabine and vinorelbine. The correlation of the results to clinical response was difficult to analyze.

The Netherlands Cancer Institute (Amsterdam), Thorax Surgery - P. Baas, J.M.M.F. Quispel-Janssen (UT: L.W.M.M. Terstappen, F.H.C. de Jongh)

HYPOTHERMAL MACHINE PERFUSION OF HUMAN DONOR PANCREAS PRIOR TO ISLET ISOLATION Maaike de Nijs BACKGROUND

RESULTS

Islet transplantation is a promising treatment for type 1 diabetes. Due to a shortage of suitable human pancreases, and the large dose of islets required for insulin independency, it is important to increase the donor pool by using extended criteria donors to obtain more pancreases. The method of preservation can contribute to enlarge the donor pool. Traditional methods of pancreas preservation lead to hypoxia of the tissue, leading to lower quality of the organ. Enhanced oxygen delivery is a key area of improvement. It is hypothesized that oxygenated hypothermic machine perfusion (HMP) of the pancreas results in a lower state of hypoxia, leading to an increased islet yield and islets with better functionality. In this study, three hours of HMP of the pancreas, after the initial cold storage (CS), was explored. In addition, the effect of HMP on the pancreas, the isolation parameters and isolated islets were monitored.

Islet yield, function and viability did not increase after three hours of additional HMP compared to CS alone. During perfusion, increasing amounts of amylase, lipase and LDH in the perfusion fluid were measured, showing washout of the enzymes from the organ. LDH showed a trend towards a plateau phase, indicating reduction of tissue damage over time. Oxygen levels in the tissue increased during perfusion as shown by an oxygen sensor. This observation was supported by the measured ATP status of the tissue after perfusion.

CONCLUSION METHOD The â&#x20AC;&#x2DC;split pancreasâ&#x20AC;&#x2122; method was developed and performed on five human donor pancreases of extended criteria donors; one half of the pancreas was three hours additionally preserved by HMP, prior to islet isolation, the other half served as control.

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Three hours of additional perfusion after CS does not augment islet yield, function and viability. However, HMP did result in a better oxygenation status of the tissue and a reduction of tissue damage as implied by ATP and LDH levels. For following studies it is suggested that longer perfusion times, and reduced preservation times will render better results.

Leiden University Medical Center, Nephrology - E.J.P. de Koning, M.A. Engelse (UT: A.A. van Apeldoorn, F.H.C. de Jongh)

THE DEVELOPMENT AND APPLICATION OF A NOVEL INTRAVITAL IMAGING PLATFORM FOR PANCREATIC ISLET TRANSPLANTATION Pim van Krieken Type 1 diabetes (T1D) is the result of early-onset autoimmune destruction of insulin producing Î˛-cells in the pancreas. A therapeutic option to manage T1D is intrahepatic islet transplantation by means of an infusion of islets in the hepatic portal vein; a treatment that is limited by available donor material. In light of this, scaffold-based tissue engineering approaches are promising. Scaffolds could facilitate use of novel, extrahepatic transplantation sites. In addition, scaffolds could provide an immuneprotective function, and aid survival and revascularization after transplantation.

In conclusion, the current imaging platform was shown to be an exciting model for diabetes research. It allows study of islet engraftment processes following transplantation at various abdominal sites, and may also be employed for immunological studies. Furthermore, it is a potent new tool to study biomaterial implants and evaluate scaffold designs.

We aimed to study the dynamic behavior of islets with and without a scaffold after transplantation in the mouse. Therefore, a novel intravital imaging technique was developed, combining two-photon microscopy and a unique imaging window. Fluorescently labeled islets were transplanted under the renal subcapsule, or in various scaffold designs on top of the dorsal back muscle of immune deficient mice. At fixed timepoints high resolution z-stacks were made of the graft or individual islets. Accordingly, islet grafts were non-invasively studied with a follow-up period of up to one month. Intravenous injection of a fluorescent dye before each imaging session showed vessel ingrowth into the graft from day 1 after transplantation under the kidney capsule. Graft revascularization could be quantified by measuring intersection volumes between vessels and islet cells in 3D reconstructions. Islet viability and Î˛-cell mass could be determined in a similar fashion. 2D quantification showed a graft survival of at least 70% after implantation in a subcutaneous pocket. In addition, a method is presented to study the dynamic behavior of islets in two subcutaneously transplanted scaffolds. Preliminary results show signs of islet cell death likely cause by hampered revascularization.

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Leiden University Medical Center, Hubrecht Institute - E.J.P. de Koning, C.J.M. Loomans, L.C.A. van Gurp (UT: A.A. van Apeldoorn, F. van der Heijden)

DEVELOPMENT OF A HYDROSTATIC PRESSURE DEVICE The effects of intermittent hydrostatic pressure on cartilage Arjanka Bandstra Osteoarthritis (OA) is the degenerative disease of synovial joints which affects more than 10% of the population. It is characterized by progressive breakdown of articular cartilage. To date there is no treatment which can cure OA or stop the degeneration process. However, joint distraction, which is still an experimental treatment, results in repair of cartilage tissue for both the ankle and the knee joint. This is demonstrated by an increase in joint space width, a decrease in pain and an increase in function. During distraction the articular surfaces of a joint are hold apart temporary with the use of an external frame. This frame provides mechanical unloading of the cartilage tissue. The mechanical unloading spares the cartilage from further wear and tear while a spring in the frame permits pressure oscillations in the synovial fluid. These hydrostatic pressure (HP) oscillations are considered important for nutrition of chondrocytes in the cartilage.

In order to test the hypothesis a HP device is developed in which cartilage and MSCs can be cocultured under distraction circumstances. Despite the fact that the device meets the requirements it has yet not been succeeded to reproduce the beneficial effect of HP on OA cartilage as was seen in earlier in vitro pressure experiments done by our research group. Simultaneously research has been done to a new coculture method which mimics the in vivo interaction between articular cartilage and MSCs in the best possible way. Besides OA cartilage MSCs are also needed for the coculture. It was investigated whether these MSCs can be isolated from the osteoarthritic synovial membrane. Isolation of MSCs from the synovial membrane was shown by CD marker expression and multipotential differentiation. Further research should first focus on reproduction of the beneficial effect of HP on OA cartilage and the further development of the coculture method before actual cocultures with cartilage and MSCs can be accomplished.

It is hypothesized that synovial fluid resident multipotent mesenchymal stromal cells (MSCs) together with the improved biomechanical environment, which is created by the distraction procedure, can play a role in the repair of cartilage. However, the exact mechanism that underlies this repair is unknown. This research and further research is aimed to investigate the effect of HP on the cartilage matrix turnover when OA cartilage and MSCs are cocultured to gain more insight in: the mechanism(s) that lead to intrinsic cartilage repair in case of joint distraction.

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University Medical Center Utrecht, Rheumatology - F.P.J.G. Lafeber, S.C. Mastbergen (UT: H.B.J. Karperien, J. Rouwkema)

THE IN VITRO OSTEOGENIC CAPACITY OF REAMER IRRIGATOR ASPIRATOR DERIVED BONE COMPARED TO ILIAC CREST CANCELLOUS BONE FOR THE PURPOSE OF AUTOLOGOUS BONE GRAFTING René van der Bel

Bone fractures are a common injury among trauma patients. Of all sustained fractures around 24% of cases involve fractures to long bones. 4 up to 12% of these fractures show disturbed bone healing resulting in a non-union. A nonunion is defined as failure of a fracture to consolidate within 9 months after injury. Impaired fracture healing and nonunion leads to long-term disability of patients and surgical intervention to overcome this problem is inevitable. Currently, iliac crest bone grafting (ICBG) is the gold standard in ABG surgery. Although the results of ICBG are generally good, the procedure presents with two significant drawbacks, including significant patient morbidity and a small graft volume. Recently the Reamer Irrigator Aspirator (RIA) has been introduced, which can be used to harvest a bone autograft by reaming the intramedullary canal overcoming the problems associated with ICBG. However, a one to one comparison of the osteogenic capacity of RIA and iliac crest grafts has not yet been described. The mesenchymal progenitor cells (MPC) are considered to be responsible for osteogenesis in vivo. However, these cell populations are inherently heterogenic and their function depends on the tissue of origin. We hypothesize that the cellular function of a bone autograft is related to its origin within the bony tissues. The main research question is stated as follows: “Is the in vitro osteogenic capacity of mesenchymal progenitor cells from RIA material greater than that of MPCs isolated from iliac crest cancellous bone?” To inverstigate this, porcine MPCs were harvested from iliac crest cancellous bone and RIA graft material. The osteogenic capacity was quantified in vitro by matrix mineralization and ALP expression analysis. Cell populations were also analyzed for mesenchymal stem cell content, using FACS.

Reamer Irrigator Aspirator in action. Copyright: Synthes Inc.

Results show significantly increased mineralized matrix deposition by RIA derived MPCs after 14 days of culture. Thus, the in vitro osteogenic capacity of MPCs from RIA material is superior to that of MPCs isolated from iliac crest cancellous bone. The underlying cause remains unclear. Factors that might play a role are: a higher concentration of MSCs in the RIA graft and the mechanical action of the RIA system.

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University Medical Center Utrecht, Traumatology - T.J. Blokhuis, B. Jansen Schuiling (UT: P. Habibovic, A. van Cappellen van Walsum)

LASER SPECKLE CONTRAST ANALYSIS FOR OBJECTIVATING THE ALLEN’S TEST AND ADVENTITIAL DISSECTION OF THE RADIAL ARTERY TO REDUCE VASOSPASM Advances of the Radial Artery Graft in Coronary Artery Bypass Surgery Stefan Sandker INTRODUCTION

CONCLUSION

Over the last two decades, the radial artery (RA) has become a routinely used graft for coronary artery bypass graft surgery (CABG). A potential disadvantage of the RA is its higher susceptibility to vasospasm compared to other arterial grafts. Prior to surgery the Allen’s test is performed to test the patency of the ulnar artery. In these studies it was investigated if laser speckle contrast analysis (LASCA) provides a more objective determination of the reperfusion time compared to the conventional Allen’s test and the effects of adventitial dissection of the RA for reducing vasospasm were determined.

LASCA is able to visualize reperfusion of the hand and measure a quick, moderate, slow reperfusion response or no reperfusion. It is technically feasible to determine the reperfusion time of the hand. LASCA could be a useful and objective tool to objectivate the Allen’s test. The adventitial dissected RA is less susceptible to vasoconstriction and more prone to vasorelaxation ex vivo. Therefore, we recommend to perform adventitial dissection of the RA graft to reduce vasospasm.

METHODS When the hand is illuminated with coherent 660nm 75mW continuous wave laser, the backscattered light will result in an interference pattern of bright and dark areas, speckles. This speckle pattern will change due to movement of red blood cells. LASCA uses these changes to visualize the perfusion during the Allen’s test on the palmar side of the hand. The reperfusion time of the hand of patients undergoing CABG (n=18) is calculated using LASCA. Following harvesting, adventitial dissection was carried out as longitudinal dissection of total adventitia and all bundles of circumferential collagen fibers on the ventral side of the RA using coronary scissors. Surplus RA segments (n=35) with and without adventitial dissection of patients undergoing CABG were collected and pairwise assessment of vasoreactivity to potassium chloride, U-46619 and acetylcholine was performed in organ bath experiments at 37oC and pH 7.4.

Perfusion image frames of a left hand of a 56 year old male patient at different time points during an Allen’s test. As can be seen the perfusion increases over time and then normalizes again. The colorbar indicates no perfusion (blue) and maximum perfusion (red). Perfusion images are made at 30 frames/sec. Each frame is averaged and set against time (blue line). A 6th degree polynomial curve fit (red line) is calculated to determine the reperfusion time.

RESULTS LASCA measurements showed a negative Allen’s test of both hands of eleven patients. Seven had a borderline reperfusion time of 5–6 seconds and/or a positive Allen’s test of one or both hands. These results were in agreement with the conventional Allen’s test. Full curve and maximal vasoconstriction to potassium chloride (p=0.015 and p=0.001) and U-46619 (p=0.048 and p=0.001) was significantly reduced for adventitial dissected RA compared to non-adventitial dissected RA. Endotheliumdependent relaxation to acetylcholine of adventitial dissected RA was significantly increased (p=0.006) compared to non-adventitial dissected RA.

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Full curve and maximal vasoconstriction to A) potassium chloride (KCL) and B) U-46619 was significantly reduced for adventitial dissected RA compared to non-adventital dissected RA. Furthermore, vasoconstriction of the internal mammary artery was significantly less compared to the RA. C) Endothelium dependent vasorelaxation to acetylcholine (ACh) was significantly increased for adventitial dissected RA compared to non-adventitial dissected RA. A,B) n=16 for RA and N=11 for IMA; C) n=22; *=p<0.05 and **=p<0.01

Medisch Spectrum Twente (Enschede), Thorax Surgery - J.G. Grandjean (UT: W. Steenbergen, A.A. van Apeldoorn - UMCG: J.H. Buikema)

IMMUNO-PROTECTIVE MEMBRANE BASED SCAFFOLDS FOR EXTRA HEPATIC ISLET TRANSPLANTATION Milou Groot Nibbelink The endocrine part of the pancreas consists of 500,000 to a million so-called islets of Langerhans. The islets comprise of different secretory cell types; α cells, β cells, δ cells, PP cells and Epsilon cells. The β cells secrete insulin, proinsulin, C peptide, and amylin. Type 1 Diabetes Mellitus is a chronic disease that manifests in children and young people (usually <30 years) and is characterized by destruction of the β cells due to an autoimmune reaction. It is known for its severe acute and long-term complications due to micro- and macroangiopathic lesions and has a significant social and economical impact. As insulin is inadequately secreted, type 1 Diabetes Mellitus patients need life-long insulin therapy and tight glucose monitoring. Patients with severe glyceamic lability, recurrent hypoglycaemia, and hypoglycaemia unawareness or an insufficient response to the insulin treatment are in need for alternative therapies. Transplantation of islets of Langerhans (containing β cells) is an experimental treatment for these patients. Over the last 10 years, research has focused on either improving immunosuppressive drug therapies or developing devices for either immuno-protection or improved islet survival. However, the ultimate solution has not yet been found. Either islets do not survive long enough or patients still need immunosuppressive drugs to avoid rejection. The aim of this project was to evaluate a multibore hollow fiber as an immunoprotective membrane based scaffold for extra hepatic islet transplantation. A modified poly(ether sulfone) (PESM) Multibore® hollow fiber from Inge AG (Greifenberg, Germany) was evaluated as a potential bioartificial pancreas. A multibore hollow fiber was proposed as a bioartificial

pancreas due to its mechanical strength and high surface area compared to single fibers. It was hypothesized that the large surface area and relatively porous structure of the PESM multibore hollow could overcome these problems. Glucose and insulin convection was determined by deadend permeation. Islets were seeded and cultured statically and dynamically to assess islet viability and functionality via histology and glucose induced insulin secretion test. Results showed that glucose and insulin pass through the membrane. In addition, a TUNEL assay showed hardly any apoptotic cells after 7 days of culture. On the down side, low insulin secretion upon glucose stimulation was detected. To really conclude if the PESM multibore hollow fiber is suitable, more experiments need to be performed.

Islet cultured for 7 days inside multibore hollow fiber. On the left the HE picture and on the right the corresponding TUNEL (green) and insulin (red) picture. 107

Leiden University Medical Center, Nephrology - E.J.P. de Koning (UT: A.A. van Apeldoorn, D. Stamatialis, S. Manohar)

PLATELET RICH PLASMA A comparative study between burn patients and healthy volunteers Greti Voortman

OBJECTIVE

RESULTS

Wound healing in burns is commonly accompanied by poor functional and cosmetic scarring. Platelet rich plasma (PRP), blood plasma containing concentrated levels of platelets, is associated with increased tissue regeneration and decreased scar formation. A randomized controlled trial is currently ongoing at the Red Cross Hospital in Beverwijk towards the effects of PRP in burn treatment. It was aimed to present growth factor quantifications and in vitro effects of PRP in addition, for part of the burn patients included. Burn patients are in a different physiological state regarding platelets. Therefore, PRP obtained from burn patients was compared to isolations from healthy volunteers.

No differences between PRP from burn patients and healthy volunteers were determined regarding platelet counts (1552 ± 608 and 1273 ± 357 109/L, respectively), and levels of P-selectin (119.7 ± 26.3 and 160.7 ± 88.1 ng/mL), PDGF-AB (18.7 ± 9.8 and 11.9 ± 8.7 ng/mL estimated) and TGF-β1 (65.6 ± 24.9 and 56.2 ± 22.3 ng/mL). Increased cell activity and diminished expression of α-SMA were observed in fibroblast cultures supplemented with PRP, more explicit for higher levels of PRP. No effect of PRP on keratinocytes was demonstrated.

METHODS AND RESULTS PRP was obtained from burn patients treated at the Red Cross Hospital (n = 5) and healthy volunteers (n =5) using Biomet’s GPS III. In addition a reference sample was acquired, prepared from blood of healthy donors. Platelet counts were assayed, and enzyme-linked immuno sorbent assay (ELISA) was performed towards levels of P-selectin, platelet derived growth factor-AB (PDGF-AB) and transforming growth factor-β1 (TGF-β1) in PRP samples. Human dermal fibroblasts and keratinocytes were cultured for four days with supplementation of PRP to the culture medium. Varying concentrations were used for reference PRP on both cell types, 5 % (v/v) of subject PRP was added to cultures of fibroblasts. Cell activity was determined by MTT assay and stress marker expression by immunohistochemical staining towards α-smooth muscle actin (α-SMA) or skin derived leukoproteinase (SKALP).

CONCLUSION PRP obtained from burn patients is suited to be used in wound healing treatment. The relation between growth factor and cytokine content of PRP and its exerted effect requires more extensive quantifications and research. Given the in vitro results beneficial effects of PRP on burn wound healing are expected, although conclusions should follow from the clinical study.

Biomet’s GPSIII system. Buffy coat represents PRP.

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Burns Center (Beverwijk) - P.P.M. van Zuijlen, B.K.H.L. Boekema (VSBN) (UT: A.A. van Apeldoorn)

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TECHNICAL MEDICINE ROTATION PROJECTS

OVERVIEW OF THE FIRST HUNDRED GRADUATES SORTED PER TRACK

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OVERVIEW MEDICAL SIGNALING NAME STUDENT

TITLE THESIS

CLINIC

GRADUATION DATE

Brons, Inge

Electrophysiological measurements on sensorimotor integration

UMCG - Clinical Neurophysiology: N.M. Maurits (UT: T. Heida, B. ten Haken)

10-07-2009

Maarseveen, Susan van

Functional and physiological outcome measures for rTMS in healthy subjects

UMCG - Clinical Neurophysiology: N.M. Maurits (UT: M.J.A.M. van Putten, A.de Keijzer)

10-07-2009

Melching, Leonie

Predicting success of vagus nerve stimulation from interictal EEG

MST - Clinical Neurophysiology: M.J.A.M. van Putten, C.C. de Vos (UT: T. Heida)

16-07-2009

Cloostermans, Marleen

Monitoring the brain in the adult ICU

MST - Clinical Neurophysiology: M.J.A.M. van Putten, C.C. de Vos (UT: T.Heida, A. de Keijzer)

17-07-2009

Braack, Esther ter

Critical Illness polyneuropathy - Electrical stimulation as possible therapy

MST - Thorax ICU & Clinical Neurophysiology: J. G. Grandjean, J.W. Vermeijden (UT: M.J.A.M. van Putten, B. ten Haken)

28-08-2009

Meijborg, Veronique

Signal analysis of ventricular fibrillation waveform patterns in intracardial electrogram recordings for predicting shock success.

UMCN - Cardiology: J.L.R.M. Smeets (UT: P.H. Veltink, A. de Keijzer)

09-10-2009

Groep, Karin van de

Optimizing the delineation of focal epilepsy. Refinement of MEG source imaging and the ictal onset detection in ECoG

UMCU - Clinical Neurophysiology: F.S.S. Leijten, G. Huiskamp (UT: M.J.A.M. van Putten, A. de Keijzer)

19-11-2009

Vrijdag, Xavier

qEEG measurements during cerebral gas embolism and the effects of hyperbaric oxygen

AMC - Hyperbaric Medicine: R.A. van Hulst (UT: M.J.A.M. van Putten, A. de Keijzer)

02-07-2010

Sharifi, Sarvi

Ambulatory monitoring of gait disorder in Parkinson’s disease

MST - Clinical Neurophysiology: J.P.P. van Vugt (UT: T.Heida, D.G.M. Zwartjes, M.J.A.M. van Putten)

13-08-2010

Doorduin, Jonne

Effects of levosimendan on diaphragm function in healthy subjects

UMCN - ICU & Clinical Neurophysiology: L.M.A. Heunks, D.F. Stegeman (UT: M.J.A.M. van Putten, B. ten Haken)

29-09-2010

Kooi, Willemijn van der

Quantification of myotonia in non-dystrophic myotonic syndromes

UMCN - Neurology & Clinical Neurophysiology: G. Drost, D.F. Stegeman (UT: M.J.A.M. van Putten, A. de Keijzer)

12-11-2010

Rohling, Lisette

Alternative method for non-invasivep positive airway pressure therapy in OSAS patients

MST - Pulmonology: M.M.M. Eijsvogel, F.H.C. de Jongh, M. Wagenaar (UT: W. Steenbergen)

22-03-2011

Klooster, Maryse van ‘t

Single pulse electrical stimulation: Quantitative EEG analysis of evoked responses in the epileptic brain

UMCU - Neurology & Clinical Neurophysiology: F.S.S. Leijten, G.J.M. Huiskamp, C.H. Ferrier (UT: M.J.A.M. van Putten, A. van Cappellen van Walsum)

07-04-2011

Abeelen, Aisha van den

Systemic and cerebral hemodynamics in Alzheimer’s disease

UMCN - Geriatrics: J.A.H.R. Claassen, J. Lagro (UT: M.J.A.M. van Putten, B.J. Zandt, A. de Keijzer)

14-06-2011

Oppersma, Eline

Pulmonary diffusion: Searching for a new standard

MST - Pulmonology: W.J.C. van Beurden, P.D.L.P.M. van der Valk, I. van der Lee (UT: F.H.C. de Jongh, A. de Keijzer)

30-08-2011

112

Overview

Ouweneel, Dagmar

Arterial pressure variation as a predictor of fluid responsiveness during spontaneous breathing

AMC - Internal Medicine & ICU: J.J. van Lieshout, B.E. Westerhof (UT: M.J.A.M. van Putten, B. Lansdorp, A. de Keijzer)

31-08-2011

Stijntjes, Marjon

Muscle ageing assessment using wrist neuromechanics

LUMC - Rehabilitation: C.G.M. Meskers, E. de Vlugt, A.B. Maier, J.H. de Groot (UT: H. van de Kooij, A.A. Stoorvogel)

05-09-2011

Meulen, Fokke van

Computer assisted grading of EEG in postanoxic patients after cardiac arrest

MST - Neurology & Clinical Neurophysiology: M.J.A.M. van Putten (UT: T. Heida, M.C. Cloostermans, B. ten Haken)

17-10-2011

Verhagen, Rens

Longitudinal EEG study on brain patterns during motor imagery in the acute stroke patient

MST - Neurology & Clinical Neurophysiology: M.J.A.M. van Putten (UT: T. Heida, A.A. Stoorvogel, C.Tangwiriyasakul)

28-02-2012

Meeks, Michelle

A novel ambulant monitoring system for lower extremity fracture healing: Development and performance evaluation of the SensiStep

UMCU - Traumatology: T.J. Blokhuis, H.R. Holtslag (UT: H.J. Hermens, L.M.G. Vrijhoef-Steuten)

06-07-2012

Bloem, Marjolein van

Brain Symmetry Index: Clinical evaluation of the Spatial and Temporal Brain Symmetry Index (BSI)

MUMC+ - Clinical Neurophysiology: V. van Kranen-Mastenbroek, J.P.H. Reulen (UT: M.J.A.M. van Putten, T. Heida)

17-08-2012

Blauw, Helga

Development of a new technique for the measurement of cerebral blood flow in patients with acute brain injury at the intensive care unit

UMCN - ICU: C. Hoedemaekers (UT: B. Lansdorp, W. Steenbergen)

07-09-2012

Duijvenboden, Stefan van

Wavelet-based markers of ventricular fibrillation in predicting defibrillation outcome

UMCN - Cardiology: J.L.R.M. Smeets, J.L. Bonnes (UT: C.H. Slump, G. Meinsma)

14-09-2012

Merckel, Eva

Predicting the response to fluid administration during pressure support ventilation

UMCN - ICU: J.Lemson, J.M.D. van den Brule (UT: B. Lansdorp, F. van der Heijden)

21-09-2012

Molenaar, Marleen

Optimization of cardiac resynchronization therapy in clincal practice during exercise

MST - Cardiology: J.M. van Opstal (UT: M.J.A.M. van Putten, B. ten Haken, W. Wesselink)

21-09-2012

Hartman, Rob

Measuring OSAS severity with an MRA with integrated sensor: Proof of concept

MST - Pulmonology: M.M.M. Eijsvogel (UT: F.H.C. de Jongh, E. Droog)

28-09-2012

Bom, Marjanne

The influence of spinal cord stimulation on pain and pain processing

MST - Clinical Neurophysiology: M.J.A.M. van Putten, C.C. de Vos (UT: R.H.J. van der Lubbe, A.A. Poot)

23-10-2012

Bronzwaer, Anne Sophie

Dynamic cardiovascular indices as parameters of brain perfusion and oxygenation in response to central blood volume depletion.

AMC - Internal Medicine & ICU: J.J. van Lieshout, B.E. Westerhof (UT: B. Lansdorp, M.J.A.M. van Putten, H.F.J.M. Koopman)

26-10-2012

Mulders, Daphne

Vagus nerve stimulation: Side effects in epilepsy during exercise and the bronchodilating effect

MST - Clinical Neurophysiology: M.J.A.M. van Putten, C.C. de Vos (UT: J.A.M. van der Palen, B. ten Haken)

30-10-2012

Kรถlgen, Renee

Baroreceptor sensitivity and cardiac output determination using the arterial waveform and electrocardiogram (not available for publication)

UMCU - Anaesthesiology: M.J.A.M. van Putten, C.C. de Vos (UT: J.A.M. van der Palen, B. ten Haken)

21-11-2012

Bakker, Akke

From data to clinical relevance with FeetB@ck

UMCU - Traumatology : H.R. Holtslag, T.J. Blokhuis (UT: H.J. Hermens)

23-11-2012

Banierink, Thijs

The prognostic value of continuous EEG and NIRS measurements in patients after cardiac arrest

MST - Clinical Neurophysiology: M.J.A.M. van Putten (UT: G. Meinsma, T. Heida, M.C. Cloostermans)

27-11-2012

113

Overview

ROBOTICS & IMAGING NAME STUDENT

TITLE THESIS

CLINIC

GRADUATION DATE

Busser, Wendy

XperGuide versus CT – A comparison between needle guidance techniques

UMCN - Radiology: L.J. Schultze Kool (UT: C.H. Slump - Philips: A. Balguid)

21-08-2009

Heijblom, Michelle

Visualising tinnitus with fMRI and EEG

MST - Clinical Neurophysiology: M. Lenders, C.C. de Vos (UT: M.J.A.M. van Putten, T. Heida, C.H. Slump)

21-08-2009

Bomers, Joyce

Da Vinci Robot. Introduction and implementation in clinical practice and comparison with laparoscopic surgery concerning view quality

UMCN - Radiology: L.J. Schultze Kool (UT: H.F.J.M. Koopman, M.J.A.M. van Putten, I.A.M.J. Broeders)

27-08-2009

Disselhorst, Jonathan

Quantification methods in dynamic and small-animal PET

UMCN - Nuclear Medicine : E.P. Visser (UT: C.H. Slump, P.H. Veltink)

28-08-2009

Veen, Linda van der

Quantitative Nuclear Cardiology: evaluation of perfusion, function and innervation

LUMC - Nuclear Medicine: M.P.M. Stokkel (UT: C.H. Slump, A. de Keijzer)

18-03-2010

Lier, Monique van

Dynamic PET and DCE-MRI: Measurements and Models

UMCN - Nuclear Medicine: L.F. de Geus-Oei, E.P. Visser (UT: C.H. Slump, A.M. van Cappellen van Walsum)

09-07-2010

Reeuwijk, Els

Dynamical ligament balancing during a TKA based on navigated ROM analysis

UMCU - Orthopedics: D.B.F. Saris (UT: H.F.J.M. Koopman, N. Verdonschot, A.A. van Apeldoorn)

17-08-2010

Harteveld, Anita

The optimization of SPECT image acquisition and reconstruction in pre-clinical and clinical applications (not available for publication)

UMCN - Nuclear Medicine: M. Gotthardt, E.P. Visser (UT: C.H. Slump, L. Moroni)

27-08-2010

Zegers, Karen

Dosimetry for radioimmunotherapy

UMCN - Nuclear Medicine: M. Gotthardt, E.P. Visser (UT: C.H. Slump, A.A. van Apeldoorn)

17-09-2010

Schouten, Martijn

Introduction of a new robotic technique for MRI-guided transrectal prostate biopsy: safety and accuracy aspects

UMCN - Interventional Radiology: J.J. Fütterer (UT: S. Misra, A. de Keijzer)

08-10-2010

Pouw, Joost

Ex vivo magnetic sentinel lymph node detection in colorectal cancer

MST - Surgery: J.M. Klaase (UT: B. ten Haken, W. Steenbergen)

02-11-2010

Siepel, Françoise

Mediastinoscopy of lymph nodes using FDG-PET/CT imaging

MST - Nuclear Medicine: W. de Bruin, J. van Dalen, E.B. van Duyn, F.H.C. de Jongh (UT: C.H. Slump)

16-11-2010

Kroes, Maarten

Needle guidance devices in the angio-suite: optimization of accuracy, radiation dose and puncture procedure time

UMCN - Radiology: L.J. Schultze Kool, F. de Lange, Y.L. Hoogeveen (UT: C.H. Slump, B. ten Haken Philips: N. Noordhoek)

11-03-2011

Kuperij, Nicole

Colonoscopy Robot: Design of a user interface

Meander Medical Center & ControlEngineering UT: I.A.M.J. Broeders, M.P. Schwartz (UT: S. Stramigioli, R. Reilink, A. de Keijzer)

18-04-2011

Hoogenboom, Martijn

Feasibility of tumor perfusion quantification with Gallium-68-citrate PET/CT imaging in liposarcoma and radiotherapy

NKI - Nuclear Medicine: W.V. Vogel, M. Sinaasappel (UT: C.H. Slump, A. de Keijzer)

21-06-2011

Jagt, Pasquelle van der

Optimization of the MRI protocol for imaging the sacral plexus and its branching nerves

UMCU/WKZ - Pediatric Urology: P. Dik (UT: B. ten Haken, W. Olthuis)

08-07-2011

Grootendorst, Diederik

Photoacoustic detection of melanoma metastases in resected human lymph nodes

NKI - Surgery: T.J.M. Ruers (UT: S. Manohar, A.A. Poot)

22-08-2011

Spliethoff, Jarich

Discrimination between benign and malignant tissue in the human prostate using diffuse reflectance and fluorescence spectroscopy

NKI - Surgery & Philips R&D: H.G. van der Poel (UT: T.J.M. Ruers, A. de Keijzer - Philips: B.H.W. Hendriks)

22-08-2011

114

Overview

Nagel, Klaas

Differentiation of prostatitis and prostate cancer using diffusion weighted imaging and MR-guided biopsy at 3T

UMCN - Interventional Radiology: J.J. FĂźtterer, F. de Lange (UT: B. ten Haken, H.F.J.M. Koopman)

26-08-2011

Verburg, Erik

MRI guided HIFU treatment of breastcancer with adjuvant MRI guided radiotherapy

UMCU - ISI: H.J.G.D. van den Bongard, K.G.A. Gilhuijs (UT: B. ten Haken, A.A. van Apeldoorn)

27-09-2011

Tije, Ellen ten

Photoacoustic elastography in breast cancer diagnostics

MST - Surgery: J.M. Klaase, F.M. van den Engh (UT: S. Manohar, M. Heijblom, A.A. van Apeldoorn)

28-09-2011

Stap, Nanda van der

The exploration of techniques for lumen detection in human colonoscopy images

Meander Medical Center: I.A.M.J. Broeders (UT: F. van der Heijden, S. Misra, R. Reilink, A.A. van Apeldoorn)

25-10-2011

Westen, Thea van

Assessment of the coating of drug-eluting stents using Atomic Force Microscopy (not available for publication)

MST - Thorax Surgery: C. von Birgelen (UT: M.L. Bennink, A.A. van Apeldoorn, K.K.M. Sweers)

30-11-2011

Alphen, Maarten van

Development of an oral tongue model

NKI - Otolaryngology: A.J.M. Balm, A.M. Kreeft (UT: F. van der Heijden, T. Heida)

06-12-2011

Potters, Wouter

Wall shear stress calculations in complex flow geometries

AMC - BioMedical Engineering & Physics: C.B.L.M. Majoie, E. van Bavel, A.J. Nederveen, P. van Ooij (UT: C.H. Slump, A.A. van Apeldoorn)

07-12-2011

Pelgrim, Gert Jan

Exploration and evaluation of quantitative myocardial perfusion modalities

UMCG - Radiology: M. Oudkerk, P.M.A. van Ooijen, R. Vliegenthart (UT: B. ten Haken, A.A. van Apeldoorn)

20-12-2011

Weg, Wietske van der

Use of prospective and retrospective, patient-specific, 3D tumor and red bone marrow dosimetry in nuclear medicine

UMCN - Nuclear Medicine: M. Gotthardt, E.P. Visser (UT: C.H. Slump, A. de Keijzer)

14-02-2012

Lutkenhaus, Lotte

Intraoperative margin assessment using diffuse reflectance spectroscopy

NKI - Surgery & Philips R&D: T.J.M. Ruers (UT: V. Subramaniam, A. de Keijzer - Philips: B.H.W. Hendriks)

27-02-2012

Haar, Harm van de

Automatic white matter bundle classification and extraction of advanced scalar measures for group studies

Donders Institute for Brain, Cognition and Behaviour: J.K. Buitelaar, M.P. Zwiers (UT: D.G. Norris, A. de Keijzer)

29-02-2012

Rijn, Floor van

Stroke Scoring: Detection of early ischemic changes on noncontrast CT scans using an atlas-based segmentation of the ASPECTS areas

AMC- Radiology & LUMC- Division of Image Processing: C.B.L.M. Majoie, H.A. Marquering (UT: C.H. Slump, A. van Cappellen van Walsum - LUMC: M. Staring, B.C. Stoel)

13-04-2012

Ruiter, Quirina de

Evaluation of fiducial markers for stereotactic body radiation therapy of colorectal liver metastases with Helical Tomotherapy

RISO - Deventer: K. Muller, A.W.H. Minken, R. Westendorp (UT: C.H. Slump, J.F.J. Engbersen)

25-05-2012

Rozeboom, Esther

Semiautomatic steering of the flexible endoscope: functional design and evaluation

Meander Medical Center - Surgery: I.A.M.J. Broeders (UT: S. Stramigioli - Demcon: M.C.J. Franken, J.G. Ruiter)

26-06-2012

Es, RenĂŠ van

Real time integration of MRI and electro anatomical catheter mapping of the left ventricle to improve cardiac stem cell delivery

UMCU - Cardiology: S.A.J. Chamuleau, F.J. van Slochteren (UT: C.H. Slump, T. Heida)

06-07-2012

Stegehuis, Paulien

Diagnosis with optical spectroscopy during in vivo human breast procedures

NKI - Surgery & Philips R&D: T.J.M. Ruers (UT: V. Subramaniam, C.H. Slump - Philips: B.H.W. Hendriks)

20-08-2012

Swaan, Abel

SpineGuide. Development of a MRI-based personalized drill guide for pedicle screws in scoliotic thoracic vertebrae

UMCU - Orthopedics: T.J.M. Ruers (UT: V. Subramaniam, C.H. Slump Philips: B.H.W. Hendriks)

28-08-2012

Verbree, Jasper

Quantitative measurements of cerebral oxygenation with MRI

AMC - Radiology : C.B.L.M. Majoie, E. van Bavel, A. Nederveen, D. Heijtel (UT: B. ten Haken)

31-08-2012

115

Overview

Langhout, Niels

Tumor specific photoacoustic imaging of lymph nodes

NKI - Surgery: T.J.M. Ruers, D.J. Grootendorst (UT: S. Manohar, H. Zwart)

03-09-2012

Overduin, Kristian

MRI-guided focal cryoablation of localized prostate cancer: Optimization of treatment monitoring and implementation at 3T

UMCN - Interventional Radiology: J.J. FĂźtterer, F. de Lange (UT: B. ten Haken, H.F.J.M. Koopman)

07-09-2012

Grootjans, Willem

Implementation of a whole body Single Photon Emission Computed Tomography protocol in clinical practice

UMCN - Nuclear Medicine: M. Gotthardt, E.P. Visser (UT: C.H. Slump, A.J.A. Winnubst)

25-09-2012

Pruim, Raimon

Functional connectivity in ADHD patients, a resting state fMRI study

Donders Institute for Brain, Cognition and Behaviour: J.K. Buitelaar, M.J.J. Mennes (UT: C.F. Beckmann, F. van der Heijden)

10-10-2012

Hertgers, Omar

Epilepsy surgery, visual field defects and Diffusion Tensor Imaging of Meyerâ&#x20AC;&#x2122;s loop: What can we learn?

VUMC - Neurosurgery: P.C. de Witt Hamer, J.C. Baayen (UT: C.H. Slump)

15-10-2012

Vijn, Thomas

Gold nanoparticles based theranostics in intra-operative imaging and ablation of HER2 overexpressing breast tumor cells.

NKI - Surgery: T.J.M. Ruers, D.J. Grootendorst (UT: R. Gill, S. Manohar)

03-12-2012

Grootendorst, Maarten

Magnetic detection of the sentinel lymph node in patients with breast cancer.

MST - Surgery: J.M. Klaase (UT: B. ten Haken, W. Steenbergen)

21-12-2012

116

Overview

RECONSTRUCTIVE MEDICINE NAME STUDENT

TITLE THESIS

CLINIC

GRADUATION DATE

Klijn, Reinoud

Bone grafting and implantology in maxillary sinus augmentation surgery

UMCN - Oral Surgery: G.J. Meijer, J.W.M. Hoekstra (UT: C.A. van Blitterswijk)

28-08-2009

Buitinga, Mijke

Nano-engineered microchips for extrahepatic islet of Langerhans transplantation

LUMC - Nephrology: E.J.P. de Koning, M.A. Engelse (UT: A.A. van Apeldoorn, C.J.M. Loomans)

25-09-2009

Griep, Lonneke

Isolation of breast cancer stem cells: A promising target for breast cancer therapies

MST- Surgery, Center for Mammacare: J.M. Klaase (UT: F. Wolbers, H.F.J.M. Koopman, J.N. Post)

20-08-2010

Walraven, MariĂŤlle

Large tubular constructs for urostomy tissue engineering

UMCN - Pediatric Urology: W.F.J. Feitz, P.J. Geutjes (UT: A.A. van Apeldoorn, M.J.A.M. van Putten)

25-02-2011

Roefs, Maaike

Exploration of novel strategies in vitro to improve engraftment in human pancreatic islet transplants

LUMC - Nephrology: E.J.P. de Koning, M.A. Engelse (UT: A.A. van Apeldoorn, B. ten Haken)

08-07-2011

Ven, Myrthe van der

Cellular processes during mechanical load: Development of an in vitro model to validate splinting strategies (not available for publication)

Burns Center Beverwijk: P.P.M. van Zuijlen, M.M.W. Ulrich (UT: A.A. van Apeldoorn, J. Rouwkema)

09-09-2011

Ymker, Marjanne

Breast cancer stem cells: from conventional analysis towards labon-a-chip drug screening

MST - Surgery, Gynaecology: J.M. Klaase, M. Brinkhuis (UT: F. Wolbers, W. Steenbergen)

09-09-2011

Peppelman, Malou

Pre-clinical model for regulatory T-cell therapy

UMCN - Immunology: I. Joosten, H.J.P.M. Koenen, P.C.M. van de Kerkhof (UT: A.A. van Apeldoorn, A. de Keijzer)

27-09-2011

Platenkamp, Karin

Recovering of blood from cardiac surgery with membrane technology

MST - Thorax Surgery: J.G. Grandjean (UT: D. Stamatialis, A.A. van Apeldoorn)

10-11-2011

Pot, Michiel

Bioprinting of organized zonal cartilage constructs

UMCU - Orthopedics: D.B.F. Saris, J. Malda, W. Schuurman (UT: L. Moroni, A. de Keijzer)

17-01-2012

Mulder, Inge

Keep moving forward: A new prosthetic device after (partial) foot amputation

UMCU - Rehabilitation: H.R. Holtslag, L. Beersma (UT: H.F.J.M. Koopman, A. de Keijzer)

24-02-2012

Jong, Thijs de

Building the bio-mechano-reactor: Design and development of a new tool for osteoarthritis research

UMCU - Rheumatology and Clinical Immunology: F.J.P.G. Lafeber, K. Wiegant, S.C. Mastbergen (UT: H.B.J. Karperien, H.F.J.M. Koopman)

29-02-2012

Doppenberg, Jason

Chondrogenic and hypertrophic differentiation of human multipotent stromal cells in alginate hydrogel constructs

UMCU - Orthopedics: D.B.F. Saris, D. Gawlitta (UT: L. Moroni)

13-03-2012

Croes, Michiel

The development of a bio-mechano-reactor for the culture of a whole stifle joint: the mechano-reactor

UMCU - Rheumatology: F.P.J.G. Lafeber, S.C. Mastbergen (UT: J. Rouwkema, W. Steenbergen)

22-05-2012

Assen, Frank

Porous microwell scaffolds for extrahepatic islet of Langerhans transplantation

LUMC - Nephrology: E.J.P. de Koning (UT: A.A. van Apeldoorn, M. Buitinga, S. Manohar)

19-06-2012

Aalbersberg, Else

Predicting and Interfering with treatment response in head and neck cancer patients

NKI - Head and Neck Surgery: C.L. Zuur (UT: J.R.M. Plass, J. Homminga)

23-07-2012

Meer, Marja ter

A novel non-invasive technique for the collection of uterine immune cells

UMCN - Immunology: H.W. van Hamersvelt, I. Joosten, R.G. van der Molen, (UT: J.R.M. Plass, J. Homminga)

30-07-2012

Saris, Anno

Dynamics of receptors of the her family

UMCG - Oncology: E.G.E. de Vries, A.G.T. Terwisscha van Scheltinga (UT: W. Steenbergen, J. Herek, C. Otto)

29-08-2012

117

Overview

Schunselaar, Laurel

Development of short term primary tumor cultures of malignent pleural mesothelioma cells for screening and development of new therapeutic compounds

NKI - Thorax Surgery: P. Baas, J.M.M.F. Quispel-Janssen (UT: L.W.M.M. Terstappen, F.H.C. de Jongh)

11-10-2012

Nijs, Maaike de

Hypothermal machine perfusion of human donor pancreas prior to islet isolation

LUMC- Nephrology: E.J.P. de Koning, M.A. Engelse (UT: A.A. van Apeldoorn, F.H.C. de Jongh)

11-10-2012

Krieken, Pim van

The development and application of a novel intravital imaging platform for pancreatic islet transplantation

LUMC - Nephrology & Hubrecht Institute: E.J.P. de Koning, C.J.M. Loomans, L.C.A. van Gurp (UT: A.A. van Apeldoorn, F. van der Heijden)

19-10-2012

Bandstra, Arjanka

Development of a hydrostatic pressure device: The effects of intermittent hydrostatic pressure on cartilage

UMCU - Rheumatology: F.P.J.G. Lafeber, S.C. Mastbergen (UT: H.B.J. Karperien, J. Rouwkema)

31-10-2012

Bel, RenĂŠ van der

The in vitro osteogenic capacity of Reamer Irrigator Aspirator derived bone compared to iliac crest cancellous bone for the purpose of autologous bone grafting

UMCU - Traumatology: T.J. Blokhuis, B. Jansen Schuiling (UT: P. Habibovic, A. van Cappellen van Walsum)

19-11-2012

Sandker, Stefan

Laser speckle contrast analysis for objectivating the Allenâ&#x20AC;&#x2122;s test and adventitial dissection of the radial artery to reduce vasospasm: Advances of the radial artery graft in coronary artery bypass surgery

MST - Thorax Surgery: J.G. Grandjean (UT: W. Steenbergen, A.A. van Apeldoorn - UMCG: J.H. Buikema)

04-12-2012

Groot Nibbelink, Milou

Immuno-protective membrane based scaffolds for extra hepatic islet transplantation

LUMC - Nephrology: E.J.P. de Koning (UT: A.A. van Apeldoorn, D. Stamatialis, S. Manohar)

13-12-2012

Voortman, Greti

Platelet rich plasma: A comparative study between burn patients and healthy volunteers

Burns Center Beverwijk: P.P.M. van Zuijlen, B.K.H.L. Boekema (VSBN) (UT: A.A. van Apeldoorn)

19-12-2012

118

Overview

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University of Twente Faculty of Science and Technology Technical Medicine P.O. Box 217 7500 AE Enschede The Netherlands P: +31-53 4893300 E: TGtnw@utwente.nl www.utwente.nl/tg

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