Cranial CT can detect atherosclerosis. Generally, in some patients, the calcification of arterial vessels is more obvious, which can be seen by cranial plain CT, for example, the calcification of middle cerebral artery or internal carotid artery is more obvious, which can be clearly seen by plain CT. However, the specific degree of stenosis is not clear on plain scan. At this time, the CTA of the head and neck vessels can be done, which is able to see the arterial stenosis of the head and neck vessels more clearly, to see whether there are obvious calcium plaques, soft plaques, or mixed plaque formation, and to check the degree of lumen stenosis, so that the degree of atherosclerosis can be more accurately determined.