Digital subtraction angiography (DSA) is a new diagnostic imaging technique used in clinical practice in recent years. The reason why angiography is used is that it can: 1. Define the type of blood supply and invasion range Angiography can show the blood supplying vessels of the tumor and the invasion range of the tumor. For example, sacrococcygeal tumors can be supplied by one side of internal iliac artery or both sides of internal iliac artery, and some tumors are supplied by lumbar artery or sacral median artery in addition to both sides of internal iliac artery, and the type of blood supply can be clarified by angiography. Determine the nature and malignant degree of the tumor Angiography can accurately determine the nature and malignant degree of the tumor according to the performance of tumor blood vessels and blood supply, so as to provide an objective basis for the formulation of treatment plan and the preparation of surgical resection. In summary, angiography is usually used to detect the distribution of bone tumor blood vessels, the main vascular structure of lesions, and to show the abnormal changes of normal blood vessels and the status of abnormal blood vessels.