Computed tomography is a diagnostic scan of the brain (and other parts of the body) made by taking cross-sectional pictures (slices) of the body with an x-ray. It is also known as a CAT scan.
CT scanners are large machines that superficially resemble MRI scanners with a central tube in which the patient lies. Computer controlled X-ray images are taken to build up a "computed tomogram" or "CT slice".
To enhance the contrast of the tomograms, the patient may sometimes be given a contrast material as a drink or by injection.
The use of CT scanners in MS has largely been replaced by MRI scans.
CT links
MS Glossary
All About Multiple Sclerosis