HearRestore: Image-guided microsurgery for hearing aid implantation
ARTORG Center
Centre Suisse d'Electronique et de Microtechnique
University of Bern
University of Bern
Tom Williamson
Inselspital Bern
Clinical Motivation >
Cochlear implantation — Insertion of electrode in to inner ear. — May restore hearing in cases of sensorineural hearing loss. — Current process (mastoidectomy) very invasive, time consuming.
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Direct cochlear access (DCA) — Drill trajectory from mastoid directly to inner ear.
Challenges >
Major difficulty due to density of vital structures in facial recess. — — — —
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Chorda Tympani
Facial nerve Chorda tympani Ossicles External auditory canal
System must be — Minimally Invasive — Accurate — Safe & Robust
Facial Nerve Trajectory 0.5 mm 2.5 - 3 mm 1.5 - 2 mm
External Auditory Canal Ossicles
Minimally Invasive Robotic Cochlear Implantation > >
> > >
Lightweight (5.5 kg) 5 DoF serial manipulator Force-torque sensor and high accuracy surgical drill mounted at wrist Non-Invasive patient fixation Optical tracking System accuracy — 0.15 ¹0.08mm
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Preparations for clinical trial underway
Project Overview Safety >
WP1: Personalized Planning > WP3: Numerical modeling of bone-instrument interaction > WP4:Functional image guidance Invasiveness
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WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
Project Overview Safety
WP1: Personalized Planning > WP3: Numerical modeling of boneinstrument interaction > WP4:Functional image guidance >
Invasiveness
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WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
WP1: Personalized Planning Goal > Ensure accurate detection of features and segmentation of structures > Likely impaired by movement of patient — Effect currently unknown — Metric necessary >
Assessment of existing segmentation accuracy — Safety of structure depends on accurate segmentation
WP1: Personalized Planning Hypothesis > Amount of motion can be estimated using image based metric Materials & Methods > Scanning phantom attached to robot > Robot placed in CBCT scanner > Rotational movements of various magnitudes during scanning > Images analyzed post-scan
WP1: Personalized Planning Results & Discussion > Motion clearly in some features of image > Metric to estimate amount of motion identified – Hausdorff distance
WP1: Personalized Planning Results & Discussion > Motion clearly in some features of image > Metric to estimate amount of motion identified – Hausdorff distance
Project Overview Safety >
WP1: Personalized Planning > WP3: Numerical modeling of bone-instrument interaction > WP4:Functional image guidance Invasiveness
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WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
WP3: Numerical modeling of bone-instrument interaction Goal > Ensure the safety of structures in the mastoid by understanding and minimizing temperature effects
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Development of a model capable of predicting temperature during drilling > Ensure safety of procedure by optimization of drill geometry and drilling protocol
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WP3: Numerical modeling of bone-instrument interaction Hypothesis > Possible to minimize effect of heating through drill geometry and protocol design Materials & Methods > Construction of test bench including thermal camera > Measurement of temperature during drilling of bone > Testing irrigation rate > Optimization of drill geometry and drilling process
WP3: Numerical modeling of bone-instrument interaction Results & Discussion > Drilling protocol defined & benchmark measurements completed > Drill geometry optimized and evaluated — Reduction in peak temperature of 10 - 20° — Rise limited to 10°with selected protocol >
Chip ejection and irrigation vital factors
Project Overview Safety >
WP1: Personalized Planning > WP3: Numerical modeling of bone-instrument interaction > WP4:Functional image guidance Invasiveness
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WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
WP4: Functional image guidance Goal > Neuro-monitoring for facial nerve preservation > Development of tools and protocols to allow detection of nerve during drilling > Development of electrical model of mastoid to improve nerve detection
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WP4: Functional image guidance DCA drill bit Hypothesis > EMG can be used as a method for preservation of the facial nerve 1 mm Materials &Methods > Development of multi-electrode DCA probe probe a3 > Conduction of animal trial with probe and comprehensive stimulation and measurement 1 d protocol
a 2
a 1
c
0.3 axial
radial
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WP4: Functional image guidance Hypothesis > EMG can be used as a method for preservation of the facial nerve Materials &Methods > Development of multi-electrode probe > Conduction of animal trial with probe and comprehensive stimulation and measurement protocol
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WP4: Functional image guidance
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Modified workflow completed 9 trajectories planned with variable distance to nerve Drilling stopped at known distances from nerve Stimulation protocol applied with all configurations Measurements repeated for all trajectories
Ma s t o id
FN 19
WP4: Functional image guidance
FN
Results & Discussion > No direct relationship between stimulus threshold and distance to nerve — Likely due to patient specific anatomy
Can reliably stop within 0.1mm > Can reliably detect if further than 0.3 mm >
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0
1
0
1
FN
-1
FN
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WP4: Functional image guidance Results & Discussion > Histopathology results show that nerve remains intact if the drill passes as close as 0.1mm to the facial nerve > Absolute last line of defense in conjunction with other safety methods
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Project Overview Safety >
WP1: Personalized Planning > WP3: Numerical modeling of bone-instrument interaction > WP4:Functional image guidance Invasiveness
>
WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
WP2: Non-Invasive Registration Goal > Minimize invasiveness of MICI procedure by removing need for fiducial screws for registration > Optimization of algorithms and benchmarking of achievable accuracy using matching of mastoid surface > Examination of A-Mode ultrasound as alternative for surface detection
WP2: Non-Invasive Registration Hypothesis > Similar registration accuracies can be achieved using non-invasive registration techniques Materials & Methods > Tracked pointer > High accuracy tracking system > 6 temporal bone specimens > Fiducial based as ground truth
WP2: Non-Invasive Registration Results & Discussion > Accuracy 0.27Âą0.09 mm at target vs ground truth > Time taken less than 3 minutes for all samples > Region of digitization limited to clinical standard > Further improvement of algorithms and workflow
Project Overview Safety >
WP1: Personalized Planning > WP3: Numerical modeling of bone-instrument interaction > WP4:Functional image guidance Invasiveness
>
WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
WP5: Nanometer Scale tracking Goal > Improve accuracy of robotic system through integration of nano tracking technology > Assessment of error sources and evaluation of system accuracy > Development of navigation demonstrator and framework
WP5: Nanometer Scale tracking Hypothesis > Reflections and refraction cause errors in light source localization Materials & Methods > Simulation of effect > Light source moving ±60° Results > Method for compensation defined > Error reduction from 0.04° to less than 0.01°
WP5: Nanometer Scale tracking >
Development of navigation demonstrator to test usability, accuracy and arrangement of SpaceCoder device. — SpaceCoder — Anatomical phantom — Tracking and navigation software
Camera
spaceCod er algorithm (x, y)
S
6D algorithm 6D spaceCoder Navigation system
Project Focus Clinical Testing Safety >
WP1: Personalized Planning > WP3: Numerical modeling of bone-instrument interaction > WP4:Functional image guidance Invasiveness
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WP2: Non-Invasive Registration Accuracy
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WP5: Nanometer Scale tracking
Preparations for First In Man
Preparations for First In Man
Preparations for First In Man
Preparations for First In Man
Thank You