Nuclear Medicine and Radiotherapy MCQs

Radiology · 25 free questions with answers & explanations.

1. A 60-year-old man with newly diagnosed prostate cancer undergoes a bone scan. The radiopharmaceutical used is Tc-99m methylene diphosphonate (MDP). Areas of active bone metastasis will appear as 'hot spots' on the scan. This uptake reflects:
2. A 25-year-old woman undergoing PET-CT for lymphoma staging receives FDG (fluorodeoxyglucose). FDG uptake in metabolically active tumor tissue occurs because:
3. A 45-year-old woman with differentiated thyroid carcinoma post-thyroidectomy is treated with radioiodine (I-131). The mechanism by which thyroid follicular cells (and metastatic deposits) concentrate I-131 is:
4. In a whole-body bone scan using Tc-99m MDP, areas of increased radiotracer uptake ('hot spots') are seen in the lumbar vertebrae of an elderly male with known prostate cancer. This is most likely due to:
5. In FDG-PET/CT, the standardized uptake value (SUV) corrected for body weight is calculated as:
6. The linear quadratic (LQ) model in radiobiology uses the alpha/beta ratio to describe tissue radiosensitivity. A tissue with a LOW alpha/beta ratio (e.g., 2-3 Gy) is characterized by:
7. In nuclear medicine, which radionuclide is used for sentinel lymph node mapping in breast cancer, and what is its mechanism of localization?
8. In PET-CT using 18F-FDG, the standard uptake value (SUV) measures glucose metabolism. Physiologically, which organ normally shows the HIGHEST 18F-FDG uptake and can mimic pathology?
9. A bone scan using Tc-99m MDP shows a 'superscan' — uniformly increased skeletal uptake with absent renal activity. What is the most common malignant cause in adults?
10. Technetium-99m (Tc-99m) is the most widely used radionuclide in nuclear medicine. It is a metastable nuclear isomer of Tc-99 with a physical half-life of:
11. A 55-year-old with a 2 cm right thyroid nodule on ultrasound undergoes a Tc-99m pertechnetate thyroid scan. The nodule appears as a 'cold' area (no tracer uptake). What percentage of cold thyroid nodules on scintigraphy are malignant, and what is the next recommended investigation?
12. In PET-CT using F-18 FDG, a standardised uptake value (SUVmax) is used to quantify metabolic activity. FDG is taken up by metabolically active cells via glucose transporters (GLUT). Which normal tissue can show HIGH physiological FDG uptake that may mimic pathology on PET-CT, requiring careful interpretation?
13. A 60-year-old with known prostate cancer and rising PSA post-prostatectomy undergoes Ga-68 PSMA PET-CT. The PSMA ligand targets prostate-specific membrane antigen. Compared to F-18 FDG PET-CT, what is the major advantage of Ga-68 PSMA PET-CT for prostate cancer?
14. Radiation therapy planning uses the concept of 'dose-volume histograms' (DVH). The linear quadratic (LQ) model describes cell survival after radiation. In fractionated radiotherapy, the alpha/beta (α/β) ratio is used to characterise tissue radiosensitivity. For late-responding normal tissues (e.g., spinal cord, kidney), the α/β ratio is:
15. On 99mTc-MIBI (sestamibi) parathyroid scintigraphy, the principle of differential washout is exploited. If there is persistent uptake on the 2-hour delayed image that was absent on the early image, this indicates:
16. The radiation dose unit Gray (Gy) measures:
17. On bone scintigraphy with 99mTc-MDP, a 'superscan' shows diffusely increased skeletal uptake with absent renal activity and suppression of soft tissue background. This pattern is MOST commonly caused by:
18. In radiotherapy, the 'linear-quadratic (LQ) model' is used to describe cell killing. The alpha/beta ratio for late-responding normal tissues (like spinal cord, rectum) compared to early-responding tissues (like mucosa, tumor) is characteristically:
19. In PET-CT using F-18 fluorodeoxyglucose (FDG), a 'flare phenomenon' may be seen after initiating treatment for bone metastases. What does this represent?
20. In radiotherapy planning, the 'planning target volume' (PTV) is defined as the:
21. Which radionuclide is used in radionuclide therapy for differentiated thyroid carcinoma, and what is its primary mode of emission used for therapy?
22. On Ga-68 DOTATATE PET-CT, which lesion type shows the HIGHEST tracer uptake due to overexpression of somatostatin receptors?
23. A patient with differentiated thyroid cancer (DTC) undergoes post-thyroidectomy radioiodine (131I) ablation. The serum thyroglobulin (Tg) is measured after TSH stimulation. If the Tg is <0.2 ng/mL with negative anti-Tg antibodies, it indicates:
24. A 50-year-old woman with well-differentiated papillary thyroid carcinoma undergoes radioiodine (I-131) therapy post-thyroidectomy. The mechanism by which differentiated thyroid cancer cells take up radioiodine is via:
25. MIBG (metaiodobenzylguanidine) scintigraphy is the preferred functional imaging for pheochromocytoma. Which radiolabelled isotope is used for MIBG therapy (as opposed to diagnosis)?