What is Computerised tomography

Computerised tomography (CT, but also known as computerised axial tomography, or CAT) provides structural images. To generate brain scans, low levels of X radiation are passed through an individual's head at a series of different angles (through 180 degree). A computer analyses each 'image' and generates what is effectively, a compound X-ray. It can provide a 'slice-by-slice' picture of entire brain, or other parts of the nervous system such as the spinal cord, if required. A drawback of CT scanning is that the contrast between more or dense tissue is not particularly good, although it can be improved by the administration of a dye (injected into the blood stream just before the scan is taken). CT scans cannot measure functional activity but they have provided valuable information about structural changes seen in the brains of some people with dementia, and about the effects and location of brain damage in general.