Cranial MRI is a scan of the brain by a magnetic resonance machine, which is a common examination method in medicine and is superior to CT in some aspects, especially in showing microscopic tissues more finely. Currently, MRI is widely used in medical examinations. Cranial MRI is mainly used to examine the presence of acute cerebral infarction, and its DWI phase is called diffusion phase, which can well distinguish acute cerebral infarction from old cerebral infarction, while CT cannot distinguish the two kinds of cerebral infarction lesions. In addition, MRI can also do angiography. Compared with CT angiography, it does not require contrast, which is a completely non-invasive test and cheaper, but the clarity of its angiography is worse than that of CT angiography. MRI can also do magnetic resonance venous system imaging, which is used to determine the presence of intracranial venous sinuses or venous system thrombosis, as well as other functional imaging to determine whether there is a reduction in intracerebral fibers, microhemorrhages, etc.