With the continuous development of CT technology and the popularization of CT equipment, CT examination has been more and more widely used in the diagnosis of various diseases. The emergence of multilayer spiral CT in recent years has improved the temporal resolution, spatial resolution and density resolution of CT images, and the development of image post-processing software has greatly improved the detection rate of lesions and enabled early diagnosis of diseases. Chest CT scan is one of the most important examination methods for lung diseases due to good density contrast of lung tissues and more sensitive display of lung diseases, which can detect small lung cancer at an early stage. However, with the upgrade of multi-layer spiral CT, volume acquisition greatly increases the amount of data and information, which provides diagnostic physicians with more high-quality image information while also increasing the X-ray radiation agent most, thus increasing the risk to patients. Therefore, how to reduce the exposure dose to the subject while ensuring that the images meet the diagnostic quality has become a very important issue and has received increasingly widespread attention. The concept of low-dose CT was first introduced by Naidich in 1990. Since then, various new techniques such as solid detectors, novel filter plates, dose protection devices, cardiac gating techniques, and various types of software for noise reduction and artifact suppression have been developed to reduce the dose to the examinees. It is generally accepted that the dose received by the examinee is more than 20% lower than the conventional dose and can be recognized as a dose reduction. The effective dose of low-dose chest CT (25mA) is 0.3-0.55mSv, which is 2-10 times lower than the standard chest CT dose and close to the X-ray chest X-ray dose, while the sensitivity and specificity are greatly improved. Low-dose chest CT scan reduces the X-ray radiation dose and radiation hazard, and at the same time can meet the requirements of diagnosis, and is currently mainly used in high-volume chest CT physical examination and screening of chest diseases. In recent years, low-dose CT scanning of the chest has been used for high-resolution computed tomography (HRCT) scans of lung diseases, which can distinguish the fine structures of diffuse lung diseases, isolated nodules and marginal conditions in the lungs more clearly, while the radiation dose of X-rays is effectively reduced.