Brain infarction mainly uses cranial CT and cranial MRI. Cranial CT plain scan is one of the most commonly used examinations for cerebral infarction and is important for the identification of cerebral infarction and cerebral hemorrhage in the early stage of onset. Within 24 hours after the onset of cerebral infarction, there is usually no obvious lesion on cranial CT, and after 24 hours of onset, a low-density lesion can appear in the infarcted area. At the cerebral infarct lesion about two weeks after the onset of the patient, due to edema reduction and phagocytic infiltration, it can appear equal density with the surrounding normal brain tissue, which is difficult to distinguish on CT, called blurring effect. Cranial MRI can detect early lesions, and several hours after the onset of cerebral infarction, MRI can show lesion areas with low signal in T1 and high signal in T2. Compared with CT examination, cranial MRI can detect brainstem and cerebellar infarcts, as well as small infarct foci.