CT and radiography have more differences, as follows: 1) the principle is different, radiography is direct projection imaging, CT is the product of the combination of X-ray and computer, CT is a cross-sectional image; 2) the clinical application is different, for example, X-ray is mainly applied to trauma patients or breast disease examination, gastrointestinal imaging, these examinations are also irreplaceable by other imaging examinations, and play an important role in clinical practice. CT examination is a cross-sectional examination with higher resolution, so it is mainly suitable for examination of small lesions, such as various diseases of the whole body, small tumors or small fractures, etc., which can be clearly diagnosed by CT; 3. The X-ray received by the film is less, less expensive, faster and more convenient, while the X-ray received by CT is larger and more expensive than the film. Therefore, in clinical practice, sometimes you can choose to film, sometimes CT is preferred, and in some cases CT examination is needed after filming to make a clear diagnosis and enable patients to receive timely treatment.