Carotid ultrasonography is a simple, non-invasive and reproducible procedure that can examine the following diseases: 1. carotid atherosclerosis, including determining whether the intima is thickened, the size and location of the plaque, whether there are ulcers on the surface of the plaque, and whether the carotid artery is narrowed and the degree of narrowing. 2. carotid aneurysm. 3. aortitis. 4. congenital carotid myofibrillar dysplasia. 5. subclavian artery piracy. syndrome. Carotid ultrasonography is mainly used to determine the nature and stability of carotid plaque in patients with cerebrovascular disease, and to provide clinical basis for early prevention and treatment of atherosclerosis. Active treatment of carotid atherosclerosis, while ensuring blood pressure and blood lipids within the normal range, and the usual low salt and low fat diet have a positive effect on the prevention of atherosclerosis.