Multilayer spiral simulation endoscopic imaging is a post-processing of image data obtained from spiral CT volume scans using fast and powerful computer functions to reconstruct a three-dimensional image of the inner surface of a cavernous organ, coolly resembling that seen by a fiberoptic endoscope. This technology has made great progress in the clinical application of organs such as colon, large blood vessels, coronary arteries, nasopharynx, larynx, trachea, bile duct, esophagus, stomach, and bladder. It is easier and more practical in trachea and bronchus. Conventional chest scan shows cross-sectional image, which lacks continuity in observation of bronchial lumen, and it is more difficult to identify bronchus with vertical direction. Simulated bronchial endoscopy is a new technique for 3D imaging of the airway, and its method is to reconstruct a simulated airway image with thin-layer spiral scan data, which can observe points placed in the trachea! The bronchus can be probed and roamed in the lumen at will, and images similar to those seen by bronchoscopy can be observed, and the images are intuitive and vivid, making this non-invasive imaging technique a new method for evaluating airway lesions. It generally requires no special preparation and is simple to perform. For elderly patients who have difficulty holding their breath, only simple breathing training is required. Since 64-layer spiral CT can be performed in a single breath-hold, the entire scanning process can be completed in a very short time of about 6-7 seconds. Only the appropriate layer thickness and pitch need to be adjusted (the thinner the layer thickness and the smaller the pitch, the clearer the image and the higher the spatial resolution). (1) Normal: smooth luminal surface, clear tracheal rings, shallow grooves between cartilage rings, smooth and sharp tracheal ridges; (2) Restricted elevation: external tracheal pressure or tumor infiltration causing the wall to expand into the lumen, smooth or uneven surface, obtuse angle with the wall, and uneven luminal deformation; (3) Stenosis: high swelling of the tracheal wall, resulting in partial or complete closure of the tracheal lumen; ( (4) intraluminal mass: the lumen is eccentrically narrowed or obstructed by a cauliflower-shaped protrusion into the tracheal lumen with an acute angle to the wall; (5) swelling: the surface of the lumen is smooth and thickened, and the shallow groove between the cartilaginous rings of the tracheobronchus disappears. Differential diagnosis: mucus plug and blood clot Dilated condensed vascular indentation Clinical applications ① foreign body in the bronchus; ② bronchial dilatation; ③ diagnosis of bronchial rupture after trauma and postoperative review; ④ in the diagnosis of endobronchial tuberculosis; ⑤ observation of bronchial anastomosis after lung transplantation; ⑥ evaluation after tracheal intubation and tracheotomy; ⑦ airway reconstruction after tumor resection; ⑧ those who are not suitable for fiberoptic bronchoscopy; ⑨ for fiberoptic training of bronchoscopists. Advantages and disadvantages of simulation endoscopy Advantages: (1) Non-invasive, safe and painless for patients. It is especially suitable for patients who cannot tolerate fiberoptic endoscopy (2) It allows visualization of the lesion from the distal end of the stenosis or obstruction. This is especially important for distal bronchial endoscopic imaging, as fiberoptic endoscopy cannot visualize distal bronchial lesions (3) Can visualize lumens that are inaccessible to fiberoptic endoscopy, such as the lumen of the pulmonary vessels (4) Can help guide fiberoptic endoscopic biopsy and treatment (5) Can change the transparency to look through the lumen to see outside the tube (6) Can be helpful in identifying whether the lesion is from the lung or the mediastinum. Disadvantages: (1) Poor tissue specificity, cannot be biopsied (2) Sensitivity to detection of flat lesions needs to be improved, for example, bronchial fibrous scars are difficult to detect due to flat lesions (3) Cannot observe color changes of the lumen lining and bacterial conditions (4) Patient breathing and movement artifacts can cause artifacts