The interval between CT examinations is determined by the purpose of the examination and the individual’s condition, as well as by the doctor’s orders. CT examinations are a type of imaging examination, mainly used as an auxiliary examination for diseases, and can improve the detection and diagnosis of lesions. In addition, this examination is also required for daily physical examination, so the interval between two CT examinations cannot be generalized. For the diagnosis of diseases in the same area, the interval between two CT examinations usually needs to be more than two weeks, the first time for diagnosing the disease, and then after a period of active cooperation with treatment, another CT examination is performed, mainly to check the effect of treatment and determine the degree of recovery of the disease. In addition, the amount of radiation produced by the X-ray beam in CT examinations does not significantly increase the incidence of cancer. For cancer patients, the time between two CT examinations may be short to facilitate timely observation of the spread of cancer cells and tissue changes, etc., and generally does not threaten health. In general, CT once or twice a year is not harmful to healthy people for the purpose of physical examination. However, since CT is still a radiological examination, it is recommended that it should not be done in non-essential cases, and if there is a need for medical examination, once a year is generally sufficient and not too much. In addition, CT examinations are much more useful for disease detection than radiation and other adverse effects, and CT is a non-invasive examination, the examination process is faster and generally does not produce significant discomfort, so patients can follow the doctor’s instructions and rest assured that the examination.