Nine CT examinations in a month are harmful to the human body. The more CT examinations in a short period of time, the higher the cumulative radiation dose to the human body, which may exceed the national safety range and adversely affect the human body. Generally no more than three CT examinations in a month is appropriate, but for some critically ill patients, the standard can be appropriately relaxed. For some special patients who must have multiple CT examinations within a short period of time due to their medical conditions, doctors need to weigh the pros and cons according to the patient’s own situation, and may appropriately perform multiple CT examinations if the benefits of diagnosis and treatment outweigh the adverse effects of CT examinations. All CT examinations should be performed under the supervision of a doctor. Whether pregnant women, infants and young children can undergo CT examinations should be based on medical advice.