kăt [computerized axial tomography], X-ray technique that allows relatively safe, painless, and rapid diagnosis in previously inaccessible areas of the body; also called CT scan. An X-ray tube, rotating around a specific area of the body, delivers an appropriate amount of X radiation for the tissue being studied and takes pictures of that part of the internal anatomy from different angles. More recent scanners have a stationary X-ray tube and use deflecting coils and special reflectors to position the X-ray beam. A computer program is then used to form a composite, readable image. CAT scanning has revolutionized medicine, especially neurology, by facilitating the diagnosis of brain and spinal cord disorders, cancer, and other conditions. Ultrafast CT, or electron beam CT, is able to take pictures in a tenth of a second. It is useful in creating images of moving parts, such as the heart, without blurring.

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