Head CT examination can be used to determine whether there is intracranial hemorrhage or ischemic lesions, occupying lesions, etc. In addition, head traumatic diseases can also be diagnosed and guided by head CT. 1. Intracranial hemorrhage or ischemic disease: head CT examination is more sensitive to intracranial hemorrhagic disease, suspected that the patient has cerebral hemorrhage can be performed emergency CT examination, to clarify the bleeding point and the amount of hemorrhage, in order to guide the emergency treatment to save the patient’s life. Head CT is not very sensitive to ischemic diseases, and can be combined with cranial MRI to improve the accuracy of diagnosis. 2. Intracranial space-occupying lesions: intracranial tumors, cysts, parasitic diseases, etc. can be clearly defined by head CT to determine the size and boundaries of the space-occupying lesions, which is of great significance to the follow-up treatment. 3. Head trauma: contusion, skull fracture, scalp hematoma can be clearly presented by CT, head CT is very valuable for the rescue of head trauma patients.