FRCR FRCR Nuclear Medicine 2 — Questions and Answers
Question 1: SPECT-CT combines which two imaging modalities?
- Single-photon emission CT and anatomic CT (Correct answer)
- PET and CT
- MRI and nuclear medicine scintigraphy
- Ultrasound and gamma camera imaging
Correct answer: Single-photon emission CT and anatomic CT
SPECT-CT fuses functional nuclear medicine (gamma camera tomography) with anatomic CT on the same device, improving lesion localization and attenuation correction.
Question 2: The 'flip-flop' phenomenon on bone scan refers to:
- Areas of initially increased uptake appearing photopenic on follow-up due to healing or flare response (Correct answer)
- Artifact from patient movement
- Alternating hot and cold spots in Paget disease
- Asymmetric uptake in bilateral joints
Correct answer: Areas of initially increased uptake appearing photopenic on follow-up due to healing or flare response
In patients responding to cancer therapy, previously photopenic lytic metastases may show increased uptake (healing response) — and vice versa — leading to the flip-flop appearance.
Question 3: Gallium-68 DOTATATE PET-CT is the preferred imaging modality for:
- Gastroenteropancreatic neuroendocrine tumors (NETs) (Correct answer)
- Prostate cancer staging
- Thyroid cancer follow-up
- Small cell lung cancer
Correct answer: Gastroenteropancreatic neuroendocrine tumors (NETs)
Ga-68 DOTATATE binds somatostatin receptors overexpressed in most gastroenteropancreatic NETs, providing superior sensitivity and resolution compared to In-111 OctreoScan.
Question 4: In myocardial perfusion imaging, which finding indicates a fixed defect rather than ischemia?
- Perfusion defect present on both stress and rest images (Correct answer)
- Defect present only on stress images that fills in at rest
- Transient ischemic dilation
- Increased right ventricular uptake on stress
Correct answer: Perfusion defect present on both stress and rest images
A fixed defect (present on both stress and rest) indicates scar tissue (prior infarction) with no viable myocardium, whereas a reversible defect (stress only) indicates ischemia.
Question 5: Which radiopharmaceutical is used to image pheochromocytoma and paraganglioma in nuclear medicine?
- I-123 or I-131 MIBG (metaiodobenzylguanidine) (Correct answer)
- Tc-99m MIBI
- Ga-68 DOTATATE
- FDG
Correct answer: I-123 or I-131 MIBG (metaiodobenzylguanidine)
MIBG is a norepinephrine analogue taken up by catecholamine-secreting tumors via the norepinephrine transporter, making it highly specific for pheochromocytoma imaging.
Question 6: The standard uptake value (SUV) in PET imaging is a measure of:
- Relative radiotracer concentration normalized to injected dose and body weight (Correct answer)
- Absolute radioactivity in a region
- Blood flow in tissue
- Metabolic rate of glucose consumption
Correct answer: Relative radiotracer concentration normalized to injected dose and body weight
SUV normalizes regional radiotracer uptake to the injected dose and patient body weight, providing a semi-quantitative measure of metabolic activity for treatment response assessment.
FRCR FRCR Nuclear Medicine 2
SPECT-CT combines which two imaging modalities?