Lung cancer is categorized into early stage lung cancer and middle and late stage lung cancer. Early stage lung cancer usually has no symptoms and shows up as a small mass on CT. In middle and late stage lung cancer, the lumps are larger and often have lymph node metastasis as well as distant metastasis. Therefore, middle and late stage lung cancer is more serious and patients have more obvious clinical symptoms, such as chest pain, cough, hemoptysis, malignant fluid in the whole body, etc. CT examination can show the severity of lung cancer, and it can find out whether the site of lung cancer is in the left lung or the right lung, in the upper lobe, the middle lobe or the lower lobe, and it can also show the shape of the lung cancer, for example, whether it is an irregular mass or a rounded shape; and it can also judge whether its size is a few millimeters or a few centimeters; and it can also judge whether its size is a few millimeters or a few centimeters. Several millimeters or several centimeters; it can also find out the relationship between the mass and the surrounding tissues, whether it invades the large blood vessels, pleura and pericardium; through CT examination, it can find out whether there are intrapulmonary metastasis, mediastinal lymph node metastasis, pleural metastasis, distant metastasis, such as liver metastasis, brain metastasis, adrenal gland metastasis, bone metastasis, and so on.