Early lung cancer lesions are small and difficult to be detected on chest X-ray, and only when the lung cancer lesions are large, they can be detected on chest X-ray. Therefore, for early detection of lung cancer, low-dose high-resolution thin-layer CT of the chest is highly recommended for screening. In the past, 90% of the patients lost the chance of surgery in the clinic, mainly because the patients neglected their condition. For tumors smaller than 1 cm or mediastinal lung cancer, which is blocked by the heart, the patient’s lesion cannot be detected by chest X-ray, which will lead to misdiagnosis in the clinic, while thin-layer CT scan can detect lesions of a few millimeters. Therefore, CT thin-layer low-dose screening of the chest has saved the lives of many patients.