There are two main ways of cranial MRA: 1, one is not to inject contrast agent through the vein, the use of blood flow and static blood vessel wall and surrounding tissue to form a contrast, and directly display the blood vessels, called direct MRA; 2, the other method for high-pressure syringe injection contrast agent, generally gadolinium preparations, has become a routine technique of MRA examination, contrast at the same time can be fast MRA imaging, similar to CTA, so called enhanced MRA. Direct MRA and enhanced MRA have their own advantages, direct MRA without contrast, easy, non-invasive, low cost, very valuable for displaying blood vessels, has become an indispensable examination method in bed, mainly used for the diagnosis of intracranial artery stenosis or occlusion, intracranial aneurysm, cerebrovascular malformation, etc. Its advantages are no intubation, convenient, time-saving, non-invasive, no need for contrast injection and no radiation. Its advantages are that it does not require intubation, convenient, time-saving, non-invasive, no contrast injection and no radiation, etc. Its disadvantages are that the signal changes are complicated, artifacts are easily produced, and the accuracy of the assessment of end vessels is not as good as that of CTA and DSA, while enhanced MRA is more reliable than direct MRA in showing the lumen of blood vessels, the artifacts of stenosis are significantly reduced, and the degree of stenosis is reflected more realistically, which is similar to that of CTA, and its reliability is even comparable to that of traditional DSA. It is comparable to CTA, and its reliability is even comparable to that of traditional DSA, and has the advantages of non-invasiveness, contrast safety, and low price compared with DSA.