Computed Tomography (CT or CAT) scan is a non-invasive test that uses a combination of X-ray and computer technology to create images that aid in the diagnosis and treatment of medical conditions. 

A CT scanner uses X-rays in a different way than a conventional X-ray machine does. Instead of taking an X-ray photograph, a CT scanner sends large numbers of X-ray beams from many directions through the part of the body being examined, records the amount of radiation that has been absorbed, and uses an internal computer to construct an image.

In CT, the computer produces a series of horizontal or vertical (or even three-dimensional) cross-sectional slice images of the body. These images offer clear pictures of all the organs in the part of the body being studied. CT scanning is able to create more fully defined pictures of the head and body than conventional X-rays and has reduced the need for invasive diagnostic procedures.