Coloured 3D computed tomography (CT) angiogram scan of the interior of the left common carotid artery of a 62 year old male patient. This is the point where the common carotid branches into the interior and exterior carotid arteries. The interior surface is irregular suggesting the presence of atheroma plaques. These fatty deposits narrow the artery and restrict the blood flow (atherosclerosis). The common carotid arteries lie on either side of the neck and carry blood to the head. Two red blood cells are seen at right.