CT and chest radiographs are two common tests used in radiology. Both examinations utilize X-rays, but CT is a tomographic scan, which has a higher resolution of density and no overlapping images of tissues and organs. Chest X-ray is an overlapping image, so the density resolution is lower, and the lesion is easily obscured and not shown more clearly than CT. However, CT examination has more layers to scan, so the radiation dose to the body is also higher. Chest films are instantaneous, and the radiation dose is very low, about the same as many natural backgrounds, and can be negligible. Moreover, the cost of CT equipment is high, so the cost of examination will be relatively high. The operation of CT is relatively complex and chest X-ray is relatively simple, so chest X-ray is usually used as a means of routine physical examination, and only when there is a problem will the patient have further CT examination.