11C-methionine PET is used to image which metabolic pathway?

• A. Glucose metabolism
• B. Amino acid metabolism
• C. Lipid metabolism
• D. Nucleotide metabolism

Answer: (B)

11C-methionine PET measures amino acid metabolism by tracking the uptake and incorporation of methionine into proteins, reflecting protein synthesis activity in tissues. Methionine is an essential amino acid transported into cells via amino acid transporters and used in translation, so areas with high protein production—such as many tumors or active brain regions—show increased tracer uptake. This differs from imaging glucose metabolism, which uses glucose analogs like FDG to reflect glycolysis; lipid metabolism would require fatty acid tracers, and nucleotide metabolism isn’t the primary signal detected with methionine. Therefore, 11C-methionine PET is best described as imaging amino acid metabolism.