In the diagnosis of pulmonary tuberculosis, clinical symptoms and signs, sputum examination of tuberculosis bacilli, imaging examination, fiberoptic bronchoscopy and lung and pleural biopsy are the basis of diagnosis, among which imaging diagnosis plays an important role in clinical diagnosis. Imaging is indispensable for the detection of lesions, differentiation from other diseases, and observation of therapeutic effects. Chest X-ray is the basic imaging method for diagnosing tuberculosis, chest CT is the common test method for differential diagnosis, and chest MRI is less used. The pathology and nature of lesions may be different for tuberculosis with the same imaging manifestations: (1) masses or spherical shadows, which may be caseous foci (tuberculoma) or proliferative tuberculosis foci surrounded by fibrous tissue; (2) lung segments or lobe shadows, which may be exudative, caseous, proliferative or endobronchial tuberculosis-induced atelectasis; (3) multiple nodules or spherical shadows in both lungs may be exudative, caseous or proliferative. (3) multiple nodules or spherical shadows in both lungs can be exudative, caseous or proliferative lesions; (4) cavity shadows, which can be caseous, fibrous or purified cavities pathologically. Cavities with spherical contents can be mycoballs, blood clots, or caseous necrotic tissue; (5) enlarged hilar and mediastinal lymph nodes can be classified as proliferative or caseous lesions. The anti-TB effect varies with the nature of the lesion, with some having significant efficacy, others less so, and some even requiring surgical treatment. Some lesions do not change dynamically under more adequate anti-TB treatment, and some even show lesion enlargement, which may be due to inadequate anti-TB, drug resistance of the tuberculosis bacilli, or other reasons. The imaging of pulmonary tuberculosis must be combined with clinical practice to properly understand the dynamic changes in imaging. Diagnosis of pulmonary tuberculosis on chest CT is based on the same basis as on chest radiograph, such as lesions occurring in the posterior segment of the upper lobe apices and the dorsal segment of the lower lobe in the form of polymorphic lesions (patchy infiltrates, nodules, spheres, cavities, etc.) is the basis for the diagnosis of secondary tuberculosis; enlarged hilar lymph nodes is the basis for the diagnosis of primary tuberculosis. Chest CT is complementary to chest X-ray in showing signs such as tuberculosis foci in hidden areas of chest X-ray and tuberculous bronchial dilatation. Chest CT can show bronchial narrowing and wall thickening in lung segments and lobes, which is helpful for the diagnosis of endobronchial tuberculosis. Spherical or mass-shaped tuberculosis foci with the help of enhancement effect, for the analysis of lesion margin and density help to differentiate from pneumonia and peripheral type lung cancer, CT observation of hilar and mediastinal lymph node enlargement than X-ray body layer does, CT density uniformity or ring enhancement helps to diagnose lymph node tuberculosis. Chest radiograph, chest CT and chest MRI are diagnosed according to the imaging performance, and the images can generally reflect the pathological changes. It is impossible to infer the nature of the lesion from the images and the pathological changes of the lesion completely, which is the limitation of the imaging diagnosis. Differentiation of pulmonary tuberculosis from other diseases is a necessary process in the diagnosis of pulmonary tuberculosis. Differentiation of pulmonary tuberculosis from pneumonia and lung cancer is a common problem. Sometimes it also needs to be differentiated from rare diseases. CT has a high density resolution, and the study of the margins and density of tuberculoma, the relationship between the lesion and the intrinsic lung structure and the enhancement effect has become a matter of interest to some authors. In the case of tuberculoma, it is more common to see calcification in the flat scan lesion, but the enhancement is not obvious in the enhanced scan or in the peripheral part of the lesion. On MRI, some TB tumors have long T1 in the center of T1WI and long T2 in T2WI, with different signals between the center and the periphery, which can also be seen in peripheral squamous carcinoma. Tuberculoma dynamics are slow, with no significant changes over 6 months, 1 year, or longer periods of time. It is worth mentioning that there are limitations in diagnostic imaging, and transthoracic aspiration biopsy should be done when there is really difficulty in diagnosis to avoid delaying the diagnosis of tumor. 2. Pulmonary tuberculosis presenting with lung segmental lobar shadow: most of the lung segmental lobar lesions are complex in composition, and proliferative lesions, caseous lesions, chronic inflammation and bronchial dilatation are seen together. Although CT has a high density resolution and MRI has a high tissue resolution, it cannot distinguish proliferative lesions, caseous lesions and chronic inflammation, but can show bronchodilation. The differentiation between this type of tuberculosis and central lung cancer should focus on the observation of lung segments and lobe bronchi, and large tracheal body, CT, CT simulation endoscopy, and MRI can observe bronchial lumen narrowing and lumen thickness. Fiberoptic bronchoscopy is an indispensable test for qualitative diagnosis, and the diagnosis can be confirmed only when pathology finds typical tuberculous lesions. 3, cavity shadowing: tuberculous cavities and caseous cavities are regular in shape with uniform wall thickness; fibrous cavities are irregular in shape and uniform in wall thickness; it is difficult to identify caseous or fibrous cavities according to cavity wall thickness. The thick-walled tuberculous cavity of 4 mm or more should be distinguished from lung cancer, and the cavity shape is more regular, which helps to distinguish tuberculosis from peripheral lung cancer. Forty percent of tuberculous cavities may have fluid leveling, which needs to be distinguished from secondary infection of pulmonary cysts. Positive sputum is the basis for confirming the diagnosis of tuberculous cavity. 4. Enlargement of hilar and mediastinal lymph nodes: the frontal and lateral views of chest radiographs suggest a certain limit of enlargement of hilar and mediastinal lymph nodes. After the superior vena cava, lateral to the aortic window, the enlarged lymph nodes of the pulmonary hilum can be shown only when they are obvious. CT and MRI are more sensitive than chest radiographs in showing enlargement of hilar and mediastinal lymph nodes. 2 cm or more of mediastinal lymph nodes with caseous necrosis in the center and tuberculous granuloma in the peripheral part can show circumferential enhancement; smaller lymph nodes with tuberculous granuloma can be uniformly enhanced. Clinical practice has shown that ring enhancement can also be seen in lung cancer lymph node metastasis and lymphoma. For the CT diagnosis of hilar and mediastinal lymph nodes, enhancement scan is necessary. The sensitivity of chest MRI for the diagnosis of enlarged hilar and mediastinal lymph nodes is not significantly different from that of chest CT. 5. Pleural effusion: When pleural effusion occurs in tuberculous pleurisy (especially in elderly patients), it needs to be differentiated from pleural metastasis of lung cancer. Tuberculous pleurisy can easily form parcels, and a few lung cancer pleural metastases can also manifest as pleural encapsulated effusions. Mild uniform thickening of the pleura, calcification, and adhesions are common manifestations of tuberculous pleurisy. It is more difficult to diagnose tuberculous pleurisy that only shows free pleural effusion and lacks clinical material. Due to the application of chest CT, it has an important role in detecting signs such as hidden sites of tuberculosis lesions, tuberculous cavities, and tuberculous bronchiectasis, and has an auxiliary role in differential diagnosis, but no CT signs have been found so far that can help qualitatively diagnose tuberculosis. Chest MRI is less commonly used in the differential diagnosis of pulmonary tuberculosis.