The application of “particle knife” for brachytherapy is to plant radioactive particles inside the tumor and use the gamma rays released from the particles to effectively irradiate and kill tumor cells for 180 days. Since the surrounding normal tissues receive only a small amount of radiation, no damage or only minor damage is caused. This is a new technology developed in the past 20 years, especially the successful development of radionuclide 125I, the progress of imaging technologies such as ultrasound and CT and the emergence of computerized three-dimensional treatment systems, which has led to the rapid development of radioactive particle brachytherapy for tumors. Radiation 125I particle brachytherapy for lung cancer is mainly for advanced non-small cell lung cancer. Depending on the patient’s condition, the location of particle implantation varies: for those who can be surgically removed, the “sandwich” method is applied to implant in the tumor bed to prevent local recurrence; for those who can only be partially surgically removed, the particles are implanted on the remaining tumor; for those who cannot be surgically removed, percutaneous puncture or fiberoptic bronchoscopy are used to implant. It is not easy to implant particles precisely by percutaneous puncture or trans-fiber bronchoscopy, because the angle and direction of needle insertion can change at any time due to rib shading and respiratory factors, and the lack of accurate lung anatomy positioning, etc. can also affect the accuracy of percutaneous puncture implantation. In addition, puncture requires high skills of the operator, otherwise, repeated puncture may easily cause different degrees of damage to lung tissues and even form pneumothorax and pulmonary hemorrhage, especially for patients with central lung cancer, and once pneumothorax occurs, the tumor will be significantly displaced. In addition, lung puncture and fiberoptic bronchoscopic implantation can also cause serious complications such as bleeding and asphyxia. Especially when the lymph node metastasis in the mediastinum surrounded by large blood vessels or the tumor in the main bronchus invades out of the trachea and fuses with its adjacent blood vessels to form a hilar mass, the slightest negligence will result in puncture injury and greatly reduce the efficacy of the whole treatment. The most critical aspect of performing radioactive particle implantation is the need for strict dosimetric assurance, and the intra-tumor radiotherapy planning system (TPS) is the only tool to ensure accurate dosimetry. -volume histogram (DVH diagram), conformal particle distribution and implantation channel. Secondly, postoperative verification of the actual number and location of implanted particles and the overlapping γ-radiation energy generated by them are effective in covering the entire tumor as well as the sub-tumor areas at the tumor margin, which must achieve the biological effect of treating the tumor while minimizing the radiation damage to the surrounding normal tissues. On the contrary, if the implantation is done randomly or blindly without strict dosimetric guarantee, it will inevitably cause radioactive damage to the normal lung tissue, heart and spinal cord around the tumor. After exploration, Prof. Chai et al. concluded that the main indications for “particle knife” brachytherapy for advanced non-small cell lung cancer are poor lung function reserve, the lung tissue to be removed exceeds the patient’s tolerance; the lesion is in the hilum and infiltrates the surrounding large vessels; the lesion extends to the mediastinum, trachea, esophagus, aorta, superior vena cava or pericardium; the tumor The tumor invades the chest wall or spine and cannot be completely surgically removed; the tumor is in the central airway lumen, and the tumor occupies one side of the main bronchial lumen below the ridge and 1/2 of the main tracheal lumen, in the middle segment tracheal lumen and in the lobe bronchial lumen; the tumor diameter is less than 6 cm. easy complications include intraoperative pneumothorax, hemoptysis, postoperative fever, particle displacement and particle wandering.