Nuclear Radiology
Core framework
Nuclear questions emphasize radiopharmaceuticals, indications, and pattern recognition. Know the tracer for each study: FDG (glucose metabolism, oncology, inflammation, myocardium), Tc-99m MDP (bone), Tc-99m sulfur colloid (liver/spleen, GI bleeding), Tc-99m mebrofenin (hepatobiliary), Tc-99m DTPA or MAG3 (renal), Tc-99m pertechnetate (thyroid, Meckel), I-123 (thyroid imaging), I-131 (therapy), and Ga-68 DOTATATE (neuroendocrine tumors).
Oncologic PET
FDG PET-CT is used for staging, restaging, and response. SUV is a semiquantitative measure that depends on injected dose, body weight, uptake time, and plasma glucose - it is not a standalone diagnostic criterion. False positives: infection, inflammation, brown fat, muscle uptake. False negatives: mucinous tumors, carcinoid, small lesions below resolution, hyperglycemia.
Cardiac and other studies
Myocardial perfusion: a fixed defect indicates scar; a reversible defect indicates ischemia. V/Q scanning is interpreted by the revised PIOPED criteria (high probability: ≥2 large mismatched segments). Bone scan: superscan (uniformly increased uptake with absent renal activity) suggests diffuse metastasis; a "cold" lesion may be lytic or avascular. Sentinel node mapping uses Tc-99m sulfur colloid.
Traps and rule of thumb
Traps: treating SUVmax as a diagnosis; forgetting that breastfeeding and pregnancy alter I-131 use; missing that a photon-deficient bone lesion can be malignant; assuming a fixed perfusion defect is ischemic.
Rule of thumb: on myocardial perfusion imaging, "fixed = scar, reversible = ischemia"; on V/Q, mismatch (ventilation normal, perfusion absent) is the hallmark of PE.