High resolution magnetic resonance image of normal brain with CAT scan.
Developed in the 1970s, CAT (or CT) scanning is a process that combines many 2-dimensional x-ray images to generate cross-sections or 3-dimensional images of internal organs and body structures (including the brain). Doing a CAT scan involves putting the subject in a special, donut-shaped x-ray machine that moves around the person and takes many x-rays. Then, a computer combines the 2-dimensional x-ray images to make the cross-sections or 3-dimensional images.
CAT scans of the brain can detect brain damage and also highlight local changes in cerebral blood flow (a measure of brain activity) as the subjects perform a task.