MRI, as an important auxiliary examination, is of great help in clarifying the diagnosis of the disease. Compared with cranial CT, MRI of the head will observe the lesions of cerebral infarction more clearly, and it is suitable for observing the lesions of lacunar infarction, as well as the lesions of cerebral stem and cerebellum. Among them is MRI diffusion imaging, which can visualize new brain infarcts. Cerebrovascular imaging by MRI utilizes the principle of flow-space effect and is able to detect atherosclerotic stenosis of cerebral arteries. In addition, MRI has important applications for herniated discs.