Different carotid blood vessels have different diameters. Carotid blood vessels include the common carotid artery, internal carotid artery and external carotid artery. The normal value of the diameter of the common carotid artery is around 6-7.5mm, the normal value of the diameter of the internal carotid artery is around 5-6mm, and the normal value of the diameter of the external carotid artery is around 4.5-5.5mm. The carotid artery is an important blood vessel connecting the human heart to the brain, and is the most important pathway for the heart to pump blood to the brain. The diameter of the common carotid artery vessels is generally a bit wider than that of the common arteries. According to the color Doppler ultrasound of the carotid artery, the thickness of the carotid artery intima-media is observed to determine whether there is a stenosis of the carotid artery. The carotid artery condition is often assessed clinically by the degree of carotid artery stenosis. If moderate or severe carotid artery stenosis occurs, it can cause severe cerebral infarction and even death, at this time, it is necessary to actively seek medical treatment, and under the guidance of a professional physician to carry out medication or surgical treatment.