Nuclear medicine

CREDIT ::

MEDICINE NUCLEAR

BHAGATH M S

2013 batch ( 4th year )

RAJEEV BISWAS

Key Points Chapter 1

GENERAL PART

Nuclear medicine: A branch of medicine concerned with the use of radioactive materials in the diagnosis and treatment of disease and medical research.

SPECT :: single photon emission computed tomography PET :: positron emission tomography Radionuclide（ unstable nuclide）: It refers to the unstable nuclei spontaneously emit radiation (such as alpha, beta ray) to form stable nuclei by decay.

Isotopes: - The isotopes of an element are having the same protons but different neutrons.

- Isotopes have similar chemical properties.

Isomers: Isomers are nuclides having the same number of protons and neutrons , but different energy state.(99mTc , 99Tc ) Nuclide: A nuclide is any individual atomic species, characterized by a specific number of neutrons and protons and energy state.

Radiation decay : > Alpha(α) decay > Beta-minus decay > Beta-plus decay > Electron capture > Gamma(γ) decay Interaction of charged particles with matter: > Ionization > Excitation > Scattering > Absorption > annihilation radiation 1|Page

Interaction of photons with matter: > Photoelectric absorption > Compton scattering > Pair production half-life > T1/2 : the half-life of the radionuclide. > a time period that the number of nuclei decreases by one-half. > Radioactivity is measured in units of becquerel (Bq).

Radiation effects: > determinate effects > stochastic effects Principles of radiation protection : > Justification > Optimization > Individual dose and risk limitation External radiation protection measures: > Time > Distance > Shielding

Chapter 2 Radionuclide Tracing Technique and

Organ Imaging the types and characteristics of the imaging: 1. static imaging the distribution of the imaging agent in organs and lesions is stable when the imaging is carried out.

2. dynamic imaging After the imaging agent is introduced into the body, the continuous imaging of the dynamic collecting organ is quickly carried out with preset speed.

3. early imaging Imaging be occurred within 2 h after injection of the imaging agent. mainly reflects the organ perfusion and early functional status.

2|Page

4.delay imaging Imaging be occurred 2 hours and above after injection of the imaging agent.

5. positive imaging (hot spot imaging) Imaging agent is mainly uptaken by the lesion tissue, and generally not or rarely by normal tissue.

The radioactivity of the lesion was higher than that of the normal tissue, show "hot spot" changes.

6. negative imaging (cold zone imaging) The imaging agent is mainly in the normal tissue uptake, while the pathological tissue is not uptaken, the performance of the radioactive distribution is sparse or defect in static imaging.

Chapter 3

Nuclear medicine instrumentation

Nuclear medicine instrumentation means some special systems, which measure and detect the amount or number of ionizations or excitation events.

The scintillation detectors are mainly composed of : > scintillators, > photomultiplier tube > preamplifier.

Positron Emission Tomography , - also called PET imaging , - is a nuclear medicine technology that uses short-lived radionuclide attached to biological molecules to allow the visualization of metabolic processes in the body by producing an image of the distribution.

Comparison of PET and SPECT

Chapter 4

Radiopharmaceuticals

DEFINITION OF A RADIOPHARMACEUTICAL 3|Page

A radiopharmaceutical is a radioactive compound used for the diagnosis and therapeutic treatment of human diseases. A radiopharmaceutical has two components: a radionuclide and a pharmaceutical.

Main features of radiopharmaceuticals: 1. Radioactive 2. Unconstant 3. Self radiation decomposition 4. Few amount Production of radionuclides: 1. Nuclear reactor 2. Cyclotron 3. Radionuclide generator Ideal radiopharmaceutical: Easy availability Short effective half-life Particle emission Suitable energy High target-to-nontarget activity ratio Radionuclidic purity: the fraction of the total radioactivity in the form of the desired radionuclide present in a radiopharmaceutical Radiochemical purity: the fraction of the total radioactivity in the desired chemical form in the radiopharmaceutical.

Chapter 5

Nuclear Endocrinology (NE)

1. MOST COMMONLY USED ISOTOPES IN THYROID :  99Tcm , Technetium-99m  131I, Radioiodine-131  123I, Radioiodine-123 99Tcm (99Tcm O4-) > pure gamma emitter > energy 140 keV > half-life 6 hours > it is not organified after trapping, it is relatively quickly released back to the blood > Used for imaging only 131I: 4|Page

> delivers both beta and gamma radiation > gamma energy is 364 keV > half-life is 8 days > used for - Thyroid uptake test - Thyroid imaging - Therapy 123I > pure gamma radiator > energy of 159 keV > half-life is 13 hours > it has ideal properties for imaging but its cost is high > used for imaging only Radioactive iodide uptake (RAIU) is the percentage of administered radioiodine incorporated by the thyroid gland. formula to calculate RAIU: Normal: GD:

Uptake increases with time and the peak at about 24hrs Uptake higher than normal and the peaktime less than 24h

Increased I-131 Uptake Diseases: Graves’ Disease Toxic multi-nodular goitre Solitary hyper-functioning nodule Decreased I-131 Uptake Diseases : Hypothyroidism: Primary or Secondary, Surgical/Radioiodine Ablation of Thyroid Thyroiditis: Acute, Subacute and Chronic Lymphocytic Renal failure, congestive heart failure: increased iodide retention Clinical indications: To determine the functional status of the thyroid gland To calculate specific doses of 131I for the treatment of hyperthyroidism To differentiate subacute or painless thyroiditis and factitious hyperthyroidism from Graves’ disease 5|Page

T3, T4 and RAIU separation, parallel Clinical contraindications: Pregnancy Nursing status Thyroid Scintigraphy: Clinical applications: Localization of Ectopic Thyroid Gland Determination of Nodule Function Differentiate Diagnosis of benign from malignant Differentiate Diagnosis of neck mass Detection of thyroid cancer metastasis Evaluation of thyroid weight Thyroid nodule:  cold nodule demonstrates decreased (absent) tracer uptake compared to the surrounding normal thyroid tissue. Malignancy is 10%~25%.  hot nodule has greater more activity than the normal surrounding thyroid tissue.  warm nodule has activity equal to the adjacent thyroid gland.

Genitourinary System 1. RENOGRAM: 3 phases of normal renogram: phase a（arrival of tracer） phase b（concentration） phase c（elimination） Quantitive analysis: peak time（tb）<4.5min half time（C1/2）<8min 15min residue rate<50% difference between peak time<1min difference between peak value<30% Glomerular filtration rate(GFR): The plasma volume(ml) filtrated through the glomerulus per minute .Normal value: 80-100 ml/min.

6|Page

2. DYNAMIC RENAL IMAGING: Radiopharmaceuticals: Glomerular filtration: 99mTc-DTPA Renal tubular epithelial secretion: 131I-OIH Seven types of abnormal curve: Prabola type Low level prolonged typeã&#x20AC;&#x20AC; Low level descending type Acute rising type High level prolonged type Stepwise drop type Small kidney type Clinical applicance of dynamic renal imaging : Renal Artery Stenosis Infection Obstruction Transplant

Chapter CPT CLINICAL APPLICATION

CARDIOVASCULAR 1. MYOCARDIAL PERFUSION IMAGING APPLICATION?

SKELETAL SYSTEM 7|Page

1. MAIN ADVANTAGE OF BONE IMAGING? > An imaging can show the whole body bone > Compared with other radiological examinations, more lesions can be found much earlier > High sensitivity 2. MAIN DISADVANTAGE OF BONE IMAGING? > Low specificity > Lack of fine anatomical structure 3. THE LESION WAS FOUND 3-6 MONTHS EARLIER THAN THAT BY X-RAY 4. MDP >

99m

Tc-MDP

> rapid blood clearance > target to background ratio is high > an ideal imaging agent

5. THREE PHASE BONE IMAGING? Dynamic bone imaging 

After intravenous injection, continuous dynamic collections are carried out at different time points,



Images of blood flow in the local bone and surrounding tissue, image of the blood pool and delayed static bone imaging,



It is divided into blood flow phase, blood pool phase, delayed phase.

blood flow phase: 

detectors be placed above lesions, the detection field of view should include the contralateral corresponding regions, in order to facilitate comparative analysis of the two sides of the image.



The velocity of 3 seconds of each frame is collected in the first 60 seconds after the bolus injection.



The blood flow mainly reflects the patency of the large blood vessels and the local arterial perfusion.

blood pool phase 

Static acquisition of a frame image is carried out within 5 min after the blood flow phase.



It mainly reflects the blood distribution of bone and soft tissue.

delayed phase 

After 3 h, the same method is performed by local bone plane or tomography;

It mainly reflects the bone salt metabolism activity of the local skeleton

6. NORMAL IMAGE > The bone structure of the whole body is clear, and the radioactive distribution is symmetrical. > Usually the radioactivity of dense bone or backbone of long bone (such as limbs) is lower, and the 8|Page

developments of loose bone and flat bone( such as skull, ribs, vertebrae, pelvis and long bones of the epiphyseal end) are relatively concentrated. > The kidneys and bladder are developed.

7. DOUGHNUT SIGN > It is a common abnormal signs of bone imaging > the center of the lesion is a radioactive defect > it is surrounded by radioactive concentration 8. SUPER BONE SCAN > The uptake of radioactive imaging agents is increased in the whole body bone , which is extensive and uniform. > Whole body bone development is abnormally increased, kidneys are usually not developed, soft tissue radioactivity is very low.

9. SUPER BONE SCAN BE SEEN IN > The mechanism may be related to diffuse reactive bone formation. > hyperparathyroidism : the whole body bone is often involved . > Malignant tumor metastasis: common in axial bone and pelvis, with uneven distribution of radioactivity or concentration range.

10. INFLUENCE FACTORS OF BONE IMAGE? (take a look) 1. drinking water Drinking more water can reduce the background radioactivity of blood tissue.

2. renal function Decreased renal function can also lead to decreased renal clearance.

3 quality of imaging agents The labeling rate of bone imaging agent should be above 95%, Otherwise the image is not clear, which will affect the evaluation of the image results 11. CLINICAL APPLICATION? (read & write points by yourself) 1. METASTATIC BONE TUMOR - Bone is a site of predilection of metastasis from malignant tumors, - Early diagnosis of metastasis is very important for staging and treatment of malignant tumors.

- Bone metastases are found 3 to 6 months earlier than those by X-ray examination.

- In clinic, whole body bone imaging is the first choice for the diagnosis of bone metastases in patients with malignant tumors.

- Bone metastatic neoplastic lesions have some characteristics: > multiple radioactive concentration lesions, among which axial bone lesions are commonly involved, 9|Page

while lesions in the distal limb bone are rarely involved. A small number of cases have single lesion. > The individual metastatic lesions are found to be osteolytic lesions, which manifest as a radioactive defect area or "cold" and "hot" mixed type changes; - Diffuse bone metastases can be super bone scan - The dynamic changes of the radioactive concentration of tumor metastasis in the treatment process can reflect the outcome of the treatment.

- Dynamic changes include: > intensity, > extent of involvement, > number of lesions, and so on.

Flicker phenomenon: In some patients who received chemotherapy,uptaking of bone metastases is also increased after chemotherapy; It does not mean that the deterioration of the disease, these patients should be checked in 6 months after treatment.

PRIMARY BONE TUMOR - Malignant and benign bone tumors are mainly present as radioactive concentration in the bone imaging.

- Distinguish between benign and malignant lesions, the role of bone imaging is limited, which is less than the X film, CT or MR. - The significance of bone imaging: 1. Early detection of lesions 2. It can accurately display the actual scope of the primary tumor invasion, which is often larger than that in the X-ray examination, so it is helpful to determine the scope of operation.

3. Help to detect metastasis from the primary tumor site 4. It is helpful to determine the recurrence and metastasis of postoperative.

- Some malignant tumors often present as a highly radioactive concentration, such as osteosarcoma and chondrosarcoma.

- But multiple myeloma can be shown as osteolytic lesions and cold zone, or the "cold" and "hot" interphase "doughnut" sign or "hot spots".

OSTEOMYELITIS - Osteomyelitis is a common infectious disease in orthopedics - X-ray examination is a routine diagnostic method.

- But X-ray findings (such as bone destruction, new bone formation, etc.) are often found in the course of the 10 | P a g e

disease after 2 weeks.

- Bone imaging: the lesion of acute osteomyelitis can manifest abnormal radioactive concentration in the occurrence of 12 ~ 48 h.

BONE TRAUMA In general, X-ray film can rapidly and accurately observe fracture rather than bone imaging.

-

The use of bone imaging of fracture is mainly in the following two aspects: 1. Some obscure fractures, occurred in sternum , sacrum, scapula, hand and foot, are usually difficult to be found in radiograph, but bone imaging is more sensitive, helpful to diagnosis.

2. monitoring and evaluation of fracture healing process.

ISCHEMIC BONE NECROSIS -

Avascular necrosis of bone Clinically, steroid induced necrosis of the femoral head is common in the long-term use of steroid

-

hormones.

Bone imaging in the diagnosis of the disease is better than X-ray, in the early symptoms, even before

-

symptoms appear, bone scan can find some of the characteristics of the abnormal changes.

Thus it is helpful for early treatment and avoid long-term complications, while X-ray is not sensitive in early stage.

The manifestation of ischemic bone necrosis in bone imaging is related to the course of the disease: 1、 Acute interruption of blood supply：The new infarction bone shows a radioactive defect.

-

2、Post infarction：At the edge of the infarct area, bone formation increased, and radioactivity uptake increased. Radioactive concentration presenting as ‘Doughnut sign’ is shown.

3、Further repair process：Bone imaging can show a much higher uptake of radioactivity METABOLIC BONE DISEASE      

-

Bone imaging has some common characteristics： Long bone uptake is increased and symmetrical.

Axial bone uptake is increased .

The radioactive uptake of the skull and mandible is particularly increased.

The ribs and the costal cartilage junction show obvious radioactivity uptake, just like "beaded“.

The shadow of the breasts is obvious, which is called "tie" sign. kidney is faint or even absent on bone scan.

Metabolic bone disease includes a variety of diseases with abnormal bone metabolism characteristics:    

Osteoporosis Osteomalacia and Paget disease Hyperparathyroidism Renal bone malnutrition, etc..

JOINT DISEASE 11 | P a g e



Arthritis can lead to increased bone imaging agent uptake when there is an inflammatory lesion in the synovial membrane, and no significant damage to the articular cartilage and adjacent bone.



In general, bone imaging can detect abnormal lesions earlier than X-ray.



Radioactive concentration is shown in the diseased joint.



Hypertrophic pulmonary joint disease is common in lung cancer.



Cortical radioactivity is symmetrically and diffusely increased in the diaphysis and metaphysis of limbs .



Long bone diaphysis cortical development is enhanced, forming a characteristic track sign or double syndrome.

Radiation around the joint is also increased due to secondary periostitis

BONE TRANSPLANTATION 

The blood supply and new bone formation of transplanted bone can be detected timely using three phase bone imaging .



Bone imaging can evaluate the survival of transplanted bone.

Tumor Imaging.

1. WHAT IS PET? > PET is the innovative medical imaging technology for detection of 1.

cancers

2.

brain disorders

3.

heart disease

> PET provides quantitative biochemical information such as 1.

metabolism

2.

blood flow, blood volume

2. WHAT IS FDG?

3. WHAT IS SUV? The SUV normalizes the amount of FDG accumulation in a region of interest (ROI) to the total injected dose and the patients body weight •

Generally, An SUV greater than 2.5 has been shown to be very sensitive and specific for malignant 12 | P a g e

lesions . â&#x20AC;˘

Formula

4. INDICATION FOR 18F-FDG PET/CT ?

1. Differentiating benign from malignant lesions 2. Searching for an unknown primary tumor 3. Staging known malignancies 4. Monitoring the effect of therapy on known malignancies 5. Determining whether residual abnormalities represent tumor or posttreatment fibrosis or necrosis 6. Detecting tumor recurrence, especially in the presence of elevated levels of tumor markers 7. Selecting the region of a tumor most likely to yield diagnostic information for biopsy 8. Guiding radiation therapy planning 9. non-neoplastic applications, such as:: evaluation of infection and atherosclerosis

13 | P a g e