PET imaging uses positron emissions from radionuclides to produce detailed functional images of which of the following?

• A. Blood flow and metabolic activity
• B. Anatomical structures like SPECT
• C. Electrical activity
• D. Bone density

Answer: (A)

Positron emission tomography provides functional images by mapping how tissues take up and process tracers, which reflects metabolic activity and blood flow. When a radionuclide decays, it emits a positron that soon annihilates with an electron, producing two gamma photons that the scanner detects in coincidence. The pattern of tracer distribution corresponds to tissue metabolism and perfusion, giving detailed functional information rather than just structure. For example, FDG-PET highlights areas of high glucose metabolism, such as active brain regions or tumors, while other perfusion tracers show blood flow. The other options point to different concepts: purely anatomical imaging (more typical of CT or MRI), SPECT’s single-photon approach, electrical activity (EEG/MEG), or bone density (DEXA).