When you go to the hospital for a check-up or consultation, many times the doctor will ask for a “chest X-ray”. As a common examination in daily life, chest X-ray is mainly to identify the heart, lungs and thorax to provide clinicians with a basis for diagnosis. The process of examining a chest film is as follows: the person stands in front of the negative of the chest film machine and presses against it, the radiation source is behind the person, the center of which is in line with the center of the person’s body and the center of the negative, and the person is allowed to take a full breath and hold it for a certain period of time to expand and fill the lungs, the radiation source starts to emit X-rays, because X-rays are a kind of penetrating rays, after the chest Because X-rays are very penetrating, they will have different attenuation when they pass through each component tissue of the chest because of the different densities of each part, and finally they will be projected on the negative to form dark and bright exposures, which can reflect the density changes of each part of the chest, and reflect chest pathologies such as pneumonia, pulmonary nodules, heart enlargement, sternal fractures, etc. Through such changes, the chest pathology can be reflected. Chest radiographs also have the limitation that it is not easy to detect some small lesions, such as early malignant pulmonary nodules. In daily practice, many people worry about radiation, but in fact, for the diagnosis and evaluation of disease effectiveness, chest X-ray several times a year is more beneficial than harmful, there is no need to talk about it. However, women of childbearing age and children need to take extra care and avoid it as much as possible.