positron emission tomography
- a technique in nuclear medicine for cross-sectional imaging that enables a noninvasive assessment and localization of metabolic activity to be made. Emission of a positron by a radioisotope results in annihilation of the positron on collision with an electron, and the creation of two gamma rays of known energy travelling in exactly opposite directions. The PET scanner has detectors on each side of the patient to detect the simultaneous arrival of the gamma rays. Images are created using reconstruction algorithm similar to CT scanning. Fluorodeoxyglucose (FDG), using fluorine-18, is used to examine glucose metabolism, and ammonia, using nitrogen-13, gives information on perfusion. Carbon-11 and oxygen-15 can also be used as radioisotopes for PET scanning. Some diseases result in decreased uptake of the radio-labelled material due to decreased function; others, including many tumours, show increased glucose metabolism and concentrate the isotope avidly. In this way functional activity of the tissues can be compared with anatomical images obtained by CT or MRI scanning. Originally used to study activity in the brain, PET is now also used for investigating the chest and abdomen. See also tomography. Compare computerized tomography.
Medical dictionary. 2011.
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Positron emission tomography — (PET) is a nuclear medicine imaging technique which produces a three dimensional image or map of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron emitting radionuclide (tracer), which is… … Wikipedia
positron-emission tomography — n tomography in which an in vivo, noninvasive, cross sectional image of regional metabolism is obtained by a usu. color coded cathode ray tube representation of the distribution of gamma radiation given off in the collision of electrons in cells… … Medical dictionary
Positron Emission Tomography — Tomographie par émission de positons Pour les articles homonymes, voir TEP. Reconstruction tridimensionnelle de la distribution de glucose marqué au fluor 18 telle que mesurée par tomographie d émission de positons La tomographie … Wikipédia en Français
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positron emission tomography — (PET) tomography accomplished by detection of gamma rays emitted from tissues after administration of a natural biochemical substance (e.g., glucose, fatty acids) into which positron emitting isotopes have been incorporated. The paths of the… … Medical dictionary
positron-emission tomography — noun Date: 1976 tomography in which a cross sectional image of regional metabolism is obtained by a usually color coded representation of the distribution of gamma radiation given off in the collision of electrons in cells with positrons emitted… … New Collegiate Dictionary
positron emission tomography — the process of producing a PET scan. Cf. PET scanner. * * * ▪ imaging technique imaging technique used in diagnosis and biomedical research. It has proved particularly useful for studying brain and heart functions and certain biochemical… … Universalium
Positron Emission Tomography — technique for creating detailed images of bodily tissues by injecting positron laden material into the body and recording the gamma rays emitted over a period of about two hours (Medicine) … English contemporary dictionary
positron emission tomography — noun tomography which relies on radioactive tracers injected into the patient, so as to detect abnormal biochemical activity. Also, PET … Australian English dictionary