Brain CTA examination is generally less risky, some people who are allergic to iodine contrast agent and have renal insufficiency are at some risk for CTA examination. Brain CTA is an intravenous injection of contrast agent, CT scanning imaging, showing the morphology of blood vessels in the brain, can be timely detection of blood vessel stenosis, malformation and other lesions. Before performing cerebral CTA, it is necessary to determine whether the patient is allergic to iodine contrast agent, whether the renal function is normal, etc. Generally, after eliminating the contraindications, careful operation can reduce the risk. Some patients may be allergic to iodine contrast agent and may have allergic reactions, which may be life-threatening in severe cases. Iodine contrast agent needs to be excreted through the kidneys and the urinary tract, and it is necessary to drink a lot of water to promote the excretion of contrast agent after CTA examination, so it is necessary to have good renal function; CTA examination in patients with severe renal insufficiency may induce renal failure, and patients should weigh the pros and cons of CTA and then choose carefully. Any examination and operation has a certain risk, it is recommended that patients consult with a specialist, and generally exclude contraindications after the examination is not dangerous.