There are two general situations for a whole body scan, including patients who have found a tumor in one organ and need to determine whether there is a tumor metastasis in other organs of the body. There are also cases where patients have severe trauma and damage to multiple organs and tissues in multiple parts of the body, and need to determine the extent and scope of the damage, requiring a whole body scan. In most cases, CT is used as a whole-body scan, but because of the high radiation level of CT on the human body, whole-body scan is not usually chosen unless in special cases. In contrast, MRI has certain restrictions on the sweep of the human body, for example, the lungs are not suitable for MRI, and ultrasound is not good for the display of the lungs as well as the head, so CT is chosen in most cases, and it is up to the doctor to decide whether a whole-body scan is needed according to the patient’s specific situation.