Angiography can examine arterial disease as well as venous disease. Arterial angiography can observe whether there is thrombus or atherosclerotic plaque in the artery, whether it causes stenosis of the lumen, where the stenosis is located, the length of the stenosis, and the relationship between the stenosis and other branch vessels, thus providing a strong clinical basis for further intervention. Venography can examine whether there is reflux in the vein, whether there is thrombus in the vein, whether the thrombus has attached to the wall, whether the thrombus has recanalized, and what is the diameter of the vein, what is the flow rate, and whether there is compression in and around the vein, resulting in stenosis, etc. Angiography can also examine complex vascular relationships such as hemangiomas and arteriovenous fistulas.