NUCLEAR TECHNIQUES FOR MEDICAL IMAGING - POSITRON EMISSION TOMOGRAPHY

Positron emission tomography (PET) is a new technique increasingly used in clinical medicine and research to create images that show physicians and scientists how effectively certain tissues are performing their physiological functions. It does this by determining the spatial distribution of radioactive nuclei that emit a positron. These nuclei are introduced to the body as ''labels'' on tracer molecules designed to probe physiological processes such as tissue perfusion or sugar metabolism. The PET scanner, based on detection techniques from nuclear and particle physics, produces three-dimensional (3-D) images using the methods of computed tomography (CT). PET isotopes are produced on-site by small cyclotrons or linear accelerators and are synthesized into highly specific chemical agents by automated systems. Physiological modeling is used to relate the PET measurements to metabolic parameters. PET plays an increasingly important role in the diagnosis of cancer, heart disease, and illnesses of the brain such as epilepsy, stroke, and the dementias. It is used as a basic research tool in studying the functional anatomy of the brain.