In clinical practice, doctors often recommend whole brain angiography according to the needs of the patient’s condition. Most of the patients have never heard of this test before, and there are often doubts: “I have already done CT and MRI, why do I need to do cerebral angiography? “. Whole brain angiography (scientific name digital subtraction angiography of cerebral vessels, DSA for short) is an X-ray examination technique widely used in clinical practice. This test can dynamically display the blood flow of each blood vessel in the skull, and even 1 mm thin blood vessels can be seen. It can not only provide the exact location of the lesion, but also a clear understanding of the extent and severity of the lesion, providing a more reliable objective basis for surgery. It is important for the diagnosis and treatment of ischemic cerebrovascular disease, intracranial aneurysm, arteriovenous malformation, aneurysm and other diseases. With the development of medical technology, CT, MRI and other non-invasive examination means are increasingly serving for clinical work. CT angiography (CTA) and magnetic resonance angiography (MRA), which are developed on the basis of CT and MRI, have been widely used in recent years because of their simplicity, non-invasiveness, low cost and low risk. However, although CTA and MRA imaging techniques have made great progress, cerebral angiography is still the gold standard for the diagnosis of cerebrovascular diseases, and has an irreplaceable and important role in cases where CTA and MRA do not reveal the problem. They also have a high probability of false positives (problems detected when there is no problem) and false negatives (problems not detected when there is a problem). Cerebral angiography, on the other hand, not only provides a more accurate diagnosis, but also reveals the location, size, severity, relationship with surrounding blood vessels, and other details that are important in establishing a treatment plan to guide further treatment. Is cerebral angiography safe? All medical procedures carry some risk. However, cerebral angiography can be done under local anesthesia, which is simple, short and relatively safe compared to other medical procedures. As a medical technology that has been in existence for decades, cerebral angiography has developed over the years with more mature technology, better equipment, stricter operation, and less and less impact on the human body from contrast agents and radiation. Neurological complications, including cerebral vasospasm, cerebral infarction, blindness, facial paralysis and neurological damage, occur at an incidence of only 0.6% to 1.9%, and the risks associated with the examination are even lower in experienced medical units. The risks of cerebral angiography are much lower than the risks of the disease itself, and the benefits to the diagnosis and treatment of the disease outweigh the risks.