How often a CT scan should be done depends on the population, but for routine checkups, once every 1 to 2 years is sufficient. Specific patients may need to have a repeat CT scan every 3 to 6 months, depending on the doctor’s instructions. In the normal population, if you have a routine physical examination of certain parts of the body, such as lung CT, it is sufficient to do it once every 1 to 2 years. However, if there is a problem with the lungs, such as a suspected high-risk nodule in the lungs, it may be necessary to review the lung CT once every 3 months, 6 months or a year. In addition, for some patients with acute cerebrovascular accidents, such as cerebral hemorrhage, early CT scanning should be done at intervals of 6 hours of head CT to understand the changes of hematoma. How often to do CT scanning intervals, according to the patient’s condition, need to be under the guidance of the doctor.