Angiography is the injection of contrast into the blood vessel. The contrast flows with the blood flow in the vessel, and the flowing contrast is collected by radiation, allowing observation of the morphology of the vessel, its course, the presence or absence of blockage, the site and extent of the lesion, and the degree of blockage. The patient will be placed under the contrast room, either in the supine position or in a special position, which needs to be chosen according to the different contrast sites. Some patients may be allergic to the contrast medium or have abnormal kidney function, so it is not recommended to use angiography to confirm the condition.