18F-FDG in PET is used to assess which metabolic process?

• A. Blood flow
• B. Glucose metabolism
• C. Protein synthesis
• D. Oxygenation

Answer: (B)

Glucose metabolism is what 18F-FDG PET measures. 18F-FDG is a radioactive form of glucose that uses the same transporters to enter cells and is phosphorylated by hexokinase, but it gets trapped after that because it cannot be further metabolized. This trapping makes the PET signal proportional to how actively cells take up and use glucose, i.e., their glycolytic activity. That’s why PET with 18F-FDG is widely used to detect tissues with high metabolic rate, such as many tumors, inflamed areas, and certain brain states.

It does not directly measure blood flow, protein synthesis, or tissue oxygenation. Blood flow imaging and perfusion studies use different tracers; protein synthesis is assessed with radiolabeled amino acids; oxygenation requires other tracers sensitive to oxygen levels.