A noninvasive technique for examining soft tissue, most commonly the brain. A narrow X-ray beam is passed through the organ repeatedly (for a full brainscan 180 separate scans are made). A computerized system analyzes the pattern of absorption at each point, which yields the data for full visualization of the organ. In a CAT-scan of the brain one can produce a visual representation of important structures including gray matter, the cerebrospinal fluid-filled cavities, blood vessels and any abnormalities like tumors, lesions, etc. Also called, simply, computerized tomography or CT-scan. See magnetic resonance imaging and position emission tomography.