FRCR FRCR Nuclear Medicine 1 — Questions and Answers
Question 1: In a bone scan, which radiopharmaceutical is most commonly used?
- Technetium-99m methylene diphosphonate (MDP) (Correct answer)
- Thallium-201 chloride
- Gallium-67 citrate
- Iodine-123 MIBG
Correct answer: Technetium-99m methylene diphosphonate (MDP)
Tc-99m MDP localizes in bone through chemisorption onto hydroxyapatite crystals at sites of increased osteoblastic activity, making it ideal for detecting bone metastases and fractures.
Question 2: FDG-PET exploits which metabolic characteristic of tumor cells?
- Increased glucose uptake and glycolysis (Warburg effect) (Correct answer)
- Increased oxygen consumption
- Enhanced protein synthesis
- Elevated lipid turnover
Correct answer: Increased glucose uptake and glycolysis (Warburg effect)
Most tumors overexpress GLUT transporters and hexokinase, trapping FDG (fluorodeoxyglucose) intracellularly after phosphorylation — this is the basis of FDG-PET oncologic imaging.
Question 3: Which nuclear medicine study is used to evaluate renal tubular function and obstruction?
- Tc-99m MAG3 renogram (Correct answer)
- Tc-99m DTPA scan
- Tc-99m DMSA scan
- Tc-99m GH scan
Correct answer: Tc-99m MAG3 renogram
MAG3 (mercaptoacetylglycine) is actively secreted by renal tubules and provides superior renal function and drainage assessment compared to DTPA in patients with reduced GFR.
Question 4: In a ventilation-perfusion (V/Q) scan, a high-probability result for pulmonary embolism requires:
- Two or more large segmental perfusion defects with normal ventilation (Correct answer)
- Any perfusion abnormality
- Matched V/Q defects
- Small subsegmental defects
Correct answer: Two or more large segmental perfusion defects with normal ventilation
PIOPED criteria define high-probability V/Q as two or more large segmental mismatched perfusion defects (perfusion defect with normal ventilation), indicating high likelihood of pulmonary embolism.
Question 5: Sentinel lymph node mapping in breast cancer most commonly uses which combination?
- Tc-99m sulfur colloid + blue dye (Correct answer)
- FDG-PET alone
- Tc-99m MIBI
- Gallium-68 PSMA
Correct answer: Tc-99m sulfur colloid + blue dye
Combined Tc-99m sulfur colloid lymphoscintigraphy and intraoperative blue dye injection maximizes sentinel node identification accuracy in breast cancer staging.
Question 6: Which radionuclide therapy is used for differentiated thyroid cancer after thyroidectomy?
- Iodine-131 (radioiodine) (Correct answer)
- Yttrium-90
- Lutetium-177
- Radium-223
Correct answer: Iodine-131 (radioiodine)
Differentiated thyroid cancers (papillary and follicular) retain iodine-uptake capability, allowing targeted ablation of remnant thyroid tissue and metastases with I-131.
FRCR FRCR Nuclear Medicine 1
In a bone scan, which radiopharmaceutical is most commonly used?