What does PET detect in tissues?

• A. Structural anatomy
• B. Biochemical and metabolic changes
• C. Electrical activity
• D. Bone density

Answer: (B)

Positron emission tomography reveals tissue function by imaging biochemical and metabolic activity using radiotracers. The tracers—often a glucose analog like FDG—accumulate in cells based on metabolic demand. Areas with high metabolic activity take up more tracer, and the emitted positrons are detected to create images that map metabolic changes, such as tumor glycolysis, brain function, or cardiac metabolism. This focuses on function rather than structure.

It doesn’t primarily show structural anatomy (that’s what CT or MRI do), nor electrical activity (that’s captured by EEG/MEG), nor bone density (measured by DEXA or CT bone assessments). In practice, PET is frequently combined with CT to align metabolic information with precise anatomy.