MRI is a very important test for acute cerebral infarction. Through MRI, it can clarify the location and size of necrotic brain tissue, as well as make certain judgments on the prognosis of patients. Compared with CT of the head, MRI has no ionizing radiation and no radioactive damage to the human body, and the image clarity is also higher, so the patient’s brain stem and posterior cranial fossa lesions can be clearly observed, which is more advantageous than CT. In the acute phase of cerebral infarction, the MRI can be used to determine the patient’s infarct site by magnetic resonance diffusion-weighted imaging within 2 hours of the onset, so the MRI in the acute phase is very widely used. MRI of the head is also important for the diagnosis of other diseases of the nervous system, such as brain demyelinating diseases and brain tumors.