In general, whole body CT is only needed when a patient has a tumor in one organ and other organs are suspected to have tumor metastasis, and another is when a patient suddenly suffers a trauma and is suspected to have injury to multiple organs or tissues in the whole body. Usually doctors will choose different imaging examinations according to the patient’s specific situation and according to different parts of the patient, for example, the patient’s head and lungs will choose CT examination, and the patient’s small organs and parenchymal organs can choose MRI or ultrasound examination, especially ultrasound examination, which is simpler, more convenient, and has no radiation to the body, and the price is lower.