Lung examination can be chosen from both X-ray and CT examination. At present, early lung cancer screening is done by low-dose spiral CT scan, so CT should be preferred for lung examination. chest X-ray, i.e., X-ray film, is quick and economical and can understand structural lesions of the heart, lungs and diaphragm, such as lung shadows, pleural effusion, inflammatory exudate, heart size, pneumothorax, etc. However, because the chest X-ray is a planar view, small lesions or pathological changes that appear early in the disease, as well as lesions behind the heart are easily missed, which requires more advanced imaging, i.e. CT scan of the chest. CT examination can detect more clearly and accurately, and locate lesions, and the CT resolution is significantly higher than that of the X-ray, and can show subtle lesions, such as tiny nodules of a few millimeters. CT can detect CT can detect lesions that do not show up on X-rays, such as lesions in the mediastinum, and the detection rate of CT is significantly higher than that of X-rays.