Cerebral infarction (CI) is a kind of ischemic stroke, accounting for about 70% of all strokes, and is a common disease of the brain caused by impaired blood supply to brain tissue. The main cause is the reduction or loss of blood flow in the cerebrovascular supply area due to thrombosis, embolism of dislodged emboli and cerebrovascular lesions in the neck and intracranial vessels, resulting in ischemia and hypoxia of the brain tissue in the blood supply area and brain tissue damage and necrosis. The clinical manifestations mainly include hemiparesis, aphasia, sensory impairment and other neurological deficits. Patients with onset <6h can be treated with timely medical thrombolysis and interventional thrombolysis, while thrombolysis is not recommended for onset >6h. Early diagnosis and treatment can avoid or reduce the damage of brain tissue and achieve better therapeutic effect; if timely diagnosis and treatment cannot be made, it will eventually lead to irreversible brain tissue necrosis and softening, and more serious sequelae such as limb paralysis, so early diagnosis and treatment of cerebral infarction directly affect the healing effect of patients, and the key to early diagnosis is to choose the appropriate examination method. Cranial CT scan and cranial MRI imaging are the current commonly used examination methods for the diagnosis of cerebral infarction. Cranial CT is more sensitive for the display of acute intracranial cerebral hemorrhage lesions, while MRI has obvious advantages for hyperacute phase and acute phase cerebral infarction. Within 12-24h of cerebral infarction, there is no change in brain tissue density in cranial CT examination, so it is difficult to make accurate diagnosis, and it often takes 24-48h to show low-density cerebral infarction foci with unclear boundaries. Therefore, patients with suspected cerebral infarction need multiple cranial CT examinations to exclude or diagnose cerebral infarction. Within 6 h after cerebral infarction, due to cytotoxic edema, the water content in the infarcted area increases by 2% to 3%, causing T1 and T2 prolongation, at which time MRI can detect the lesion, which is manifested as a cerebral infarct lesion with low signal in T1WI and high signal in T2WI; a few minutes after the occurrence of cerebral infarction, the energy metabolism of brain tissue is damaged, Na-K/ATPase and other ion pumps fail, and a large amount of extracellular water enters intracellularly, causing an increase in intracellular water molecules and a decrease in extracellular water molecules, resulting in restricted diffusion of water molecules, and high-signal cerebral infarct lesions (restricted diffusion) can be detected on DWI sequences as early as 30 minutes later, with reduced ADC values and abnormal signals that can last for 3-5 days, showing that DWI is highly sensitive and specific for the display of hyperacute phase cerebral infarct lesions, and can detect hyperacute phase and At the same time, cranial angiography (MRA) can also clarify the obstruction, stenosis site and degree of the lesion vessels causing cerebral infarction. In summary, MRI has good soft tissue resolution and can clearly display cerebral infarction foci, which is significantly better than CT in the diagnosis of hyperacute and acute cerebral infarction, while cranial angiography (MRA) can also clarify the lesion vessel condition of cerebral infarction. Routine cranial MRI imaging should be performed in a timely manner, and DWI sequences should be used as mandatory sequences to detect hyperacute and acute cerebral infarction at an early stage and avoid missed diagnosis and misdiagnosis. Figure 1 Cranial MRI imaging (composed of four small images) of a patient with acute cerebral infarction, in which T1WI, T2WI and FLAIR faintly show an abnormal signal next to the left lateral ventricle, while the DWI sequence (the last small image in the lower right corner) clearly shows a nodular high-signal cerebral infarction foci next to the left lateral ventricle; Figure 2 Cerebrovascular imaging (MRA) of a patient with acute cerebral infarction, showing stenosis and occlusion of the left middle cerebral artery. Figure 3 Cranial CT scan of a patient with cerebral infarction, showing a nodular low-density cerebral infarct in the right basal ganglia region.