Lung cancer is currently one of the most common malignant tumors around the world, and in several major cities in China, lung cancer has become the most common malignant tumor among male adults. Early detection, diagnosis and early treatment are the only way to reduce the death rate of lung cancer and increase the long-term survival rate of lung cancer patients. At present, when many patients come to the hospital with clinical symptoms such as persistent cough, coughing blood and chest pain, most of the tumors detected by routine X-ray chest examination are already in the middle and late stages, and the 5-year survival rate is low after surgery, radiotherapy, chemotherapy or biological treatment. Therefore, for early stage lung cancer, especially small tumors located in the peripheral lung fields, which often have no conscious symptoms, timely detection through health screening is required. The traditional method is X-ray chest examination, but it is often missed for two reasons: (1) the contrast between small peripheral lung cancer and the lung tissue around the lesion is poor; (2) the lung tissue overlaps with the mediastinum, heart and diaphragm on the orthopantomogram. In contrast, spiral CT can detect lesions located at anatomical dead ends or missed lesions on chest films due to overlapping tissue structures by high-speed, continuous data acquisition and cross-sectional tomography, which significantly improves the detection ability of small nodular lesions in the lung and is of great significance for early detection of lung cancer. However, the X-ray radiation dose of conventional spiral CT examination is high, which is not in line with the principle of radiological optimization if used as lung cancer screening for “healthy people”, therefore, low radiation dose scanning is more in line with the requirements of health screening. Low-dose spiral CT is a CT examination technique based on the lowest scan range and radiation concentration that can detect small nodules in the lung. Many citizens have a misconception that the amount of X-ray radiation from CT scans can be harmful and are often reluctant to undergo low-dose spiral CT examinations. In fact, conventional CT examinations due to high X-ray radiation dose, a chest CT X-ray radiation dose is equivalent to 60-100 times the dose of X-ray chest film; while low-dose spiral CT through the method of reducing the tube current and tube voltage, after thin-layer reconstruction, highlighting its advantages of fast scanning speed, low dose, high detection rate, scanning radiation dose is significantly lower than conventional CT. because the lung is air-containing tissue, with Because the lung is an air-containing tissue, it has naturally good density contrast, and the quality of the image generated by using low-dose scanning is not significantly reduced. Since the mid-1990s, several universities and research institutions in Japan and the United States have started to study the application of low-dose spiral CT. The results showed that more lung cancers, especially early-stage lung cancers, could be detected with low-dose spiral CT scans. Studies on low-dose spiral CT scans, X-ray chest films, and sputum exfoliative cell microscopy for comparative screening of lung cancer showed that sputum exfoliative cells found significantly lower positive rates for small lung cancer diagnosis than low-dose spiral CT scans, and the sensitivity and specificity of low-dose spiral CT scans were significantly higher than that of X-ray chest films. Compared with conventional dose CT scanning, low-dose spiral CT scanning technology does not reduce the image quality of solid lung lesions, diffuse lung lesions, the two have similar diagnostic correct rate. ”Low-dose” is an examination method, a new concept rather than a new technology! At present, the second- and third-level hospitals in all districts of Shanghai have various types of spiral CT, which can obtain high-quality chest images at 10%-30% of the conventional dose, which is sufficient for lung tumor screening and greatly reduces the radiation dose. Currently, our hospital (2014) has one dual source CT and one Gem CT, two 64-row CTs, and one 16-row and 4-row CT each. At present, all multi-row CTs can be implemented by technical engineers to perform low-dose CT scans in accordance with unified technical standards during relevant examinations, and the detection rate of small and early lung cancers less than 1 cm in diameter reaches more than 80% through low-dose spiral CT examinations. Among the screened early-stage lung cancer patients, 80% to 90% can be cured through minimally invasive surgical resection without further radiotherapy and chemotherapy. Therefore, medical experts at home and abroad suggest that for people with high risk of lung cancer and areas, units or individuals with conditions, low-dose spiral CT screening should be actively carried out once a year regularly to improve the clinical diagnosis and treatment of early-stage lung cancer.