After a head injury, a head CT is done at that time to clarify the intracranial changes, then a head CT is done for three days, and then a head CT is done for seven days after the injury, because it is necessary to clarify the changes in the condition in order to detect the condition early, and if there is indeed discomfort and changes in the condition, a CT test is needed at any time and anywhere. The main purpose of CT at that time is to check whether there is bleeding and other manifestations of lesions. 3 days to review CT, mainly to exclude the formation of delayed intracranial hematoma. The CT of the head should be repeated in about 7 days to clarify whether there is brain tissue swelling in the skull and the degree of swelling. If the corresponding condition is stable within 7 days, there is basically no too special change in the later stage of the disease, so 7 days is a very critical period.