Computerized tomography

Computerized tomography
Pictures of structures within the body created by a computer that takes the data from multiple X-ray images and turns them in pictures. The computerized tomography (CT) scan can reveal some soft-tissue and other structures that cannot be seen in conventional X-rays. Using the same dosage of radiation as that of an ordinary X-ray machine, an entire slice of the body can be made visible with about 100 times more clarity with the CT scan. The tomograms ("cuts") for CT are usually made 5 or 10 mm apart. The CT machine rotates 180 degrees around the patient's body. The machine sends out a thin X-ray beam at 160 different points. Crystals positioned at the opposite points of the beam pick up and record the absorption rates of the varying thicknesses of tissue and bone. The data are then relayed to a computer that turns the information into a 2-dimensional cross-sectional image. The CT scanner was invented in 1972 by the British engineer Godfrey N. Hounsfield (later Sir Godfrey) and the South African (later American) physicist Alan Cormack. CT scanning was in general use by 1979, the year Hounsfield and Cormack were awarded the Nobel Prize in Medicine or Physiology for its development. The CT scan is also known as the CAT (computerized axial tomography) scan.

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computerized tomography n COMPUTED TOMOGRAPHY abbr. CT

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a form of X-ray examination in which the X-ray source and detector (CT scanner) rotate around the object to be scanned and the information obtained can be used to produce cross-sectional images (see cross-sectional imaging) by computer (a CT scan). A higher radiation dose is received by the patient than with some conventional X-ray techniques, but the diagnostic information obtained is far greater and should outweigh the increased risk. CT scanning can be used for all parts of the body, but is particularly useful in the head, chest, and abdomen. The data obtained can be used to construct three-dimensional images of structures of interest. See also multislice CT scanning, spiral CT scanning.

Medical dictionary. 2011.

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