Two CTs in one day If a CT can now perform a combined chest, abdomen and pelvis scan, which counts as one test, then another CT is not recommended on the same day. However, if a chest examination is done in the morning and an abdominal examination is done in the afternoon, this will be counted as two examinations, but the total radiation dose is much less than that of a combined chest, abdomen and pelvis scan. The country has a special CT radiation dose requirements, in 2012 when the introduction of radiation metrology standards for X-ray protection, for different parts of the examination, the radiation dose is strictly regulated. When doing the examination, the patient should be examined according to the range of dose control, which basically will not exceed the national standard. There are some patients if the condition requires, for example, patients with brain hemorrhage, CT at 6 o’clock in the morning, when the bleeding is very small, but in the ward observation will find that the patient’s symptoms are getting more and more serious, this time it is necessary to re-examine the CT, in order to understand the scope of the bleeding, to understand the progress of the disease, and to decide the next step to determine whether it is necessary to do a craniotomy, hematoma drainage, and so on. At this point, two CT examinations must be done without any consideration of radiation safety beyond the fact that it is helpful in the diagnosis and treatment of the disease. In short, the doctor will keep the radiation dose within safe limits and there is no need to consider radiation safety beyond what is helpful for diagnosis and treatment of the disease.