CT scanning—sometimes called CAT scanning—is a noninvasive medical test that helps physicians diagnose and treat medical conditions. CT scanning combines special x-ray equipment with sophisticated computers to produce multiple images or pictures of the inside of the body. These cross-sectional images of the area being studied can then be examined on a computer monitor, printed or transferred to a CD.

CT scans of internal organs, bones, soft tissue and blood vessels provide greater clarity and reveal more details than regular x-ray exams.

How is a CT scan done?
CT stands for computerised tomography, and CAT for computerised axial tomography (sometimes the word computed is used instead of computerised). The CT scanner looks like a giant thick ring. Within the wall of the scanner there is an X-ray source. Opposite the X-ray source, on the other side of the ring, are X-ray detectors. You lie on a couch which slides into the centre of the ring until the part of the body to be scanned is within the ring. The X-ray machine within the ring rotates around your body. As it rotates around, the X-ray machine emits thin beams of X-rays through your body, which are detected by the X-ray detectors.

What is a CT scan used for?
A CT scan can be done on any section of the head or body. It can give clear pictures of bones. It also gives clear pictures of soft tissues which an ordinary X-ray test cannot show, such as muscles, organs, large blood vessels, the brain and nerves. The most commonly performed CT scan is of the brain – to determine the cause of a stroke, or to assess serious head injuries. Other uses of a CT scan include:

To detect abnormalities in the body, such as tumours, abscesses, abnormal blood vessels, etc, when they are suspected by symptoms or other tests.
To give a surgeon a clear picture of an area of your body before certain types of surgery.
To pinpoint the exact site of tumours prior to radiotherapy.
To help doctors find the right place to take tissue samples (biopsies).