In general, NCCN guidelines recommend annual low-dose spiral CT of the lungs for people at high risk for lung cancer. The high-risk group is defined as: 1. 55-74 years of age, who are smoking or have quit smoking for less than 15 years and have a smoking index greater than 30 pack-years. 600 annual cigarettes. 2. Those who are older than 50 years old, with smoking index greater than 20 pack-years. 400 annual cigarettes, and combined with one of the following conditions: history of tumor; history of lung disease; family members with lung cancer; radon exposure and occupational exposure to carcinogenic substances. The above high-risk groups of lung cancer are recommended to undergo low-dose spiral CT (LDCT) annually for a minimum of 3 years (the optimal duration is unknown), while routine LDCT is not recommended for other intermediate and low-risk groups. Depending on the CT findings, different management measures are taken: 1. No pulmonary nodules: Annual LDCT for at least 3 years (optimal duration not yet known). 2. Solid or partially solid pulmonary nodules (nodules without benign calcification, fatty or inflammatory manifestations): (1) ≤4mm, annual LDCT for at least 3 years (the optimal duration is not yet known). (2) >4-6mm, LDCT after 6 months, if no growth, LDCT after 12 months, still no growth, LDCT every year for at least 2 years (optimal duration not yet known). (3) >6-8mm, review LDCT after 3 months, if there is no growth, review LDCT after 6 months, no change then review LDCT after 12 months, still no change, review LDCT every year for at least 2 years (the optimal duration of years is not known). (4) >8mm, consider PET/CT examination, if lung cancer is suspected, surgery or biopsy; if lung cancer is not considered, dynamic observation as above. In the above cases under dynamic observation, if nodules are found to grow, surgical resection is recommended. (5) If endobronchial nodules are found, review LDCT after 1 month, if they do not subside, do fiberoptic bronchoscopy for clarification. 3.Find pulmonary ground glass shadow (GGO) or other non-solid nodules (no clear benign indication): (1) <5mm, repeat CT after 12 months, if stable, LDCT every year for at least 2 years (the optimal duration is not known). (2) 5-10 mm, CT review after 6 months, if stable, annual LDCT for at least 2 years (optimal duration not yet known). (3) >10mm, review LDCT after 3-6 months, if stable, LDCT can be reviewed after 6-12 months, or biopsy or surgical resection. If the nodules are found to be enlarged or solid during the above dynamic observation, they should be surgically removed except for those with diameters <5mm, which can be considered for dynamic review of LDCT in 3-6 months.