CT scan of the chest is a routine method of examining the chest. CT scan can be used to diagnose most of the lesions in the chest, and it mainly shows the lung window and mediastinal window, in which the lung window can show the condition of lung tissue, and the mediastinal window can show the structure of the mediastinum and whether there are lesions, and also can show the bone changes in the sternum. The parts of the chest that can be examined by CT plain scan mainly include: 1. Pleura and intrapleural organs: CT plain scan can examine the general shape of the lung, trachea, bronchus and pulmonary artery, and also can initially determine whether there are pathological changes such as injury, inflammation, infection and tumor. Pleural lesions, such as pleurisy, pleural effusion, pneumothorax, etc., can also be observed. 2. Bony tissue of the chest: Regarding the presence or absence of abnormalities in the structure of the sternum, thoracic vertebrae, ribs and rib cartilage, the presence or absence of fractures, foreign bodies, tumors, deformities, and the presence or absence of occupying lesions, etc., can all be observed by CT of the chest. For diseases requiring chest surgery, CT plain examination can also help determine the location of the surgical incision; 3. Mediastinum and internal mediastinal tissues: Tumors in the mediastinum can also be screened by CT plain examination, such as lymphoma, thymoma, esophageal tumor, neuroma, etc.; 4. Heart: CT plain examination can show whether there is any change in the size of the heart, and can also exclude the presence of pericardial effusion and other heart diseases. It can also observe whether there are changes in the morphology of the aorta of the heart, which can show aortic diseases such as aortic aneurysm and aortic coarctation. 5.Other: If the position of CT scan of the chest is relatively low, it can also observe organ lesions of the digestive system such as liver and spleen, which can provide a certain basis for the diagnosis of related diseases.