CT examination has a high clinical diagnostic value for common and multiple diseases of the lung. The scope of lung CT examination includes: 1, lesions of trachea and main bronchus: such as inflammatory lesions, foreign bodies, tumors, blood clots, etc.; 2, lung diseases: such as proliferative lesions, fibrous lesions, pulmonary nodules, pulmonary cavities, tumors, etc.; 3, lesions of pleura and hilar: such as pleural effusion, pneumothorax, fluid pneumothorax, pleural adhesions, etc.; 4, changes of mediastinum and diaphragm: mediastinal lesions and lesions of diaphragm itself, etc.