HEALTH & DISEASE A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site positron emission tomography (PET) scanning PET scanner. Credit: Yale University A medical diagnostic technique based on the detection of positrons emitted by labeled substances introduced into the body. PET scanning produces three-dimensional images that reflect the metabolic and chemical activity of tissues being studied. PET images therefore give information about function as well as structure. How PET scanning works Substances that take part in biochemical processes in the body are labeled with radioisotopes (radioactive forms of elements, such as carbon-11, nitrogen-13, or oxygen-15). These substances are injected into the bloodstream and are taken up in greater concentrations by areas of tissue that are more metabolically active. In the tissue, the substances emit positrons, which, in turn, release photons (particles of light). It is the detection of these photons that actually forms the basis of PET scanning. By surrounding the patient with an array of detectors linked to a computer, the origin of the photons can be computed and a picture built of the distribution of the radioisotope. What PET scanning is used for PET scanning is particularly valuable for investigating the brain. It is used for detecting tumors (which are more or less metabolically active than surrounding tissues), for locating the origin of epileptic activity within the brain, and for beaming brain function in various mental illnesses. Related category    • HEALTH AND DISEASE Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP