Blocked artery. Three-dimensional computed tomogr- aphy (CT) scan of an artery affected by atheroscl- erosis. An atheroma plaque (yellow) is seen in the carotid artery, one which supplies the brain. Atheroma is an unhealthy fatty deposit which forms on the inner walls of blood vessels. Plaques are more common in those with high cholesterol levels, smokers, those with high blood pressure and the obese. Lack of blood to the brain may cause a transient ischaemic attack or even a stroke, which may be fatal. CT scans use X-rays to obtain slice images through the body, which can be combined to create a 3-D endoscopic view. This allows non- invasive study of the inside of the body.