POSITRON EMISSION TOMOGRAPHY

(PET) imaging technique used in diagnosis and biomedical research. It has proved particularly useful for studying brain and heart functions and certain biochemical processes involving these organs (e.g., glucose metabolism and oxygen uptake). In PET, a chemical compound "labeled" with a short-lived, positron-emitting radionuclide of carbon, oxygen, nitrogen, or fluorine is injected into the body. The activity of such a radiopharmaceutical is quantitatively measured throughout the target organs by means of photomultiplier-scintillator detectors. As the radionuclide decays, positrons are annihilated by electrons, giving rise to gamma rays that are detected simultaneously by the photomultiplier-scintillator combinations positioned on opposite sides of the patient. The data from the detectors are analyzed, integrated, and reconstructed by means of a computer to produce images of the organs being scanned.