Which tracer is used to assess metabolic activity in PET imaging, including cancer and epilepsy?

• A. 11C-Choline
• B. 13N-ammonia
• C. 18FDG
• D. 68Ga-DOTATATE

Answer: (C)

Metabolic activity in PET imaging is assessed with a tracer that mirrors how cells use glucose. The best pick is 18F-labeled fluorodeoxyglucose, because it behaves like glucose: it is taken up by glucose transporters and, once phosphorylated, becomes trapped inside cells as FDG-6-phosphate. This trapping allows visualization of tissues with high glycolytic activity. In cancer, many tumors show increased glucose metabolism, making FDG-PET a sensitive tool for detecting and staging disease. In epilepsy, FDG-PET helps localize epileptogenic regions by revealing areas with abnormal glucose metabolism that correspond to dysfunctional networks. Other tracers target specific pathways—for example, choline reflects membrane synthesis and is used in particular cancer types, ammonia mainly represents perfusion imaging, and Ga-DOTATATE binds somatostatin receptors to image neuroendocrine tumors—so they don’t provide the broad metabolic activity mapping that FDG-PET offers.