Computed axial tomography

Computed Axial Tomography (also known as CAT, Computer Assisted Tomography, Computed Tomography, CT, or body section roentgenography) is the process of using digital processing to generate a three-dimensional image of the internals of an object from a series of two-dimensional x-ray axial images. The individual x-ray axial slice images are taken using a x-ray tube that rotates around the object taking many scans as the object is gradually passed through the gantry. The multiple scans from each 360 degree sweep are then processed to produce a single cross-section.

It is used in medicine as a diagnostic tool, often to detect and visualize soft tissue abnormalities. Commonly scanned areas are the brain, the chest, the abdomen, and the pelvis. To improve the quality of soft tissue images a contrast material such as barium (administered orally or rectally) or intravenous iodinated contrast is sometimes used. Although most common in healthcare the process is used for non-invasive examination in many fields.

The system was invented in 1972 by Godfrey Newbold Hounsfield[?] of EMI Laboratories using gamma rays. Allan McLeod Cormack[?] of Tufts University independently invented the same process and they shared a Nobel Prize in medicine in 1979. The first scanner took several hours to acquire the raw data and several days to produce the images. Modern multi-slice CT systems can collect twelve 8mm slices in a single second and complete and display an entire chest scan in ten seconds.

The word tomography is derived from the Greek tomos (slice) and graphia (describing).

Compare Magnetic Resonance Imaging, Nuclear Magnetic Resonance, positron emission tomography, Ultrasonic Imaging[?].

See also: Hounsfield scale[?]