According to statistics, about 40% of patients with malignant tumors can be clinically cured, of which local control of the tumor contributes about 90%. Although surgical resection is the preferred means of local control of tumors, most patients cannot be operated due to late discovery, and some patients with surgical possibilities are unwilling to be operated or cannot tolerate surgery for various reasons. Therefore, targeted therapy technology, which focuses on local tumor cell inactivation, is developing rapidly and has become one of the leading directions for tumor treatment in the 21st century. Percutaneous minimally invasive targeted therapy for tumors borrows the concept of missile guidance technology to accurately kill local tumor cells in the target area and “resect” the tumor with equal volume, while minimizing the damage to the surrounding normal tissues. Intertissue implantation of radioactive particles is one of the important minimally invasive targeted treatment means. According to the statistics, about 50%~70% of tumor patients need to receive radiotherapy at different stages of the disease.At the end of the 20th century, the precise radiotherapy technology with the core of precise positioning, precise planning and precise treatment can be realized, but the application is very limited for the tumor patients with large mobility not easy to be fixed, unavoidable sensitive tissues in the periphery, large volume, deeper site and more foci; at the same time, the application is very limited; at the same time, the application of radiological particle inter-tissue implantation is one of the most important minimally invasive targeted therapies. At the same time, due to the high-energy rays of external radiotherapy inevitably cause certain damage to normal tissues and organs around the tumor, and the segmented irradiation to avoid serious damage to normal tissues leads to the repair of sub-lethal damage of the tumor, which makes it difficult for the therapeutic dose of external radiotherapy to reach the lethal dose of the tumor. Intertissue implantation of radioactive particles is a kind of brachytherapy, which has the advantages of precise radiotherapy and has a wider scope of application than the current mainstream technology of external radiotherapy, such as conformal intensity modulation and stereotactic radiotherapy. after the 1980s, the miniaturization of low-activity radioactive sources and the wide application of computer technology in the field of clinical medicine, especially in the field of medical imaging, have led to the wide application of intertissue implantation technology for the treatment of tumors in clinics. tumors has been widely used in the clinic. Its basic practice is to put the closed radioactive source with certain specifications and activity into the tumor tissue locally by minimally invasive method to carry out high-dose radiation therapy to achieve the therapeutic purpose. At present, the commonly used radioactive source is 125I particles, which is characterized by: sealed and non-polluting; low radiation energy, low-energy gamma rays of 27Kev~35Kev; small radius of radiation (1.7cm); and exponential reduction of radiation energy and distance, which is convenient for conformity. I. Advantages of inter-tissue permanent implantation of radioactive particles: 1. Wide range of application. It can be used for: ① solid tumors in all parts of the body and some tumors in cavity organs. ② Tumors of various tissue types, including tumors insensitive to external radiotherapy or those who are resistant to radiotherapy and chemotherapy, and those who fail in treatment. ③ Radiotherapy for various tumors whose adjacent tissues are sensitive to radiation. ④ Radiotherapy for tumors of various shapes and sizes. ⑤ Good pain relief for bone metastatic pain. 2. Effectiveness. It is one of the treatments with the best local control rate of tumor at present.3. Safety. Generally speaking, clinically applied 125I particles are almost insufficient to cause clinically visible therapeutic effects or side effects for most of the tumors or normal tissues other than 1cm, which minimizes the dose received by normal tissues, so the local radiotherapy side effect rate is extremely low, and no systemic side effect has been reported, which is a good therapeutic safety.4. Continuous irradiation. Continuous irradiation of radioactive particles in tumor tissues has the effect of promoting apoptosis of tumor cells in all periods, so that the value-added tumor cells will be reduced continuously. 5. Overcoming oxygen dependence. Due to the reduction of the initial dose rate, the oxygen enhancement ratio is reduced, i.e., the amount of oxygen required by the radiation to kill the tumor cells is reduced, which in turn partially overcomes the resistance of the tumor oxygen-depleted cells to radiation. 6. Highly conformal. Since the radioactive particles are planted in the corresponding position inside the tumor according to the design of the treatment plan, the isodose curve formed by the particles is distributed according to the morphology of the tumor and its tissue structure, so as to achieve a high degree of conformity between the dose distribution and the tumor. This conformity is not affected by the movement of the lesion.7. Intensity-modulated radiotherapy in the real sense. According to the tissue structure of each part of the tumor, implantation of radioactive particles with different activities and densities in different parts of the tumor can achieve non-uniform distribution of the dose in the tumor according to the needs, and at the same time, additional implantation can be carried out according to the situation of regular review, so as to realize intensity-modulated radiotherapy in the real sense. 8. Repeatability. Generally, one-time radioactive particle implantation for smaller tumors can achieve ideal treatment effect, and for larger tumors or tumors with poor treatment effect of one-time implantation, supplemental implantation can be repeated to achieve the purpose of dose compensation, so as to ensure that the radiation dose rate inside the tumor can be maintained at a high level without any limitation of the total dose. 9. compatibility. The rate of local side effects is very low and no significant systemic side effects have been found, so it can be used in conjunction with other local and/or systemic therapies before and after the treatment. 10. Lower requirements for patients’ physical condition. Since radioactive particle tissue implantation is a minimally invasive and safe treatment method, it can be applied to most patients, especially to elderly patients or those who cannot tolerate surgery, radiotherapy and chemotherapy, and there are generally no obvious complications after the operation. The basic difference between intertissue implantation of radioactive particles and external irradiation 1. the activity of radioactive source is small, and the therapeutic distance is short, which is easy to be protected. 2. no special protection shielding is needed, and most of the energy of the particles can be absorbed by the tissues. 3. considering less limiting factors of tolerance of the surrounding tissues, due to the fact that the radioactive source is in the tumor, the dose of the tumor is far more than that of the normal tissues. 4. continuous irradiation, which can significantly increase the radiological and biological effects, and completely destroy DNA double-strandedness, and cause no obvious damage to the DNA and chemotherapy. Continuous irradiation, significantly improve the biological effect of radiation, complete destruction of DNA double-strand breaks, and greatly improve the therapeutic gain ratio. 5. Highly conformal, reducing the incidence of tissue damage. Indications of radioactive particle implantation: particle implantation is mainly used for tumors with strong repair ability of sub-lethal radioactive damage; tumors with poor reoxygenation process or high proportion of oxygen-depleted cells after radiation therapy; tumors with high differentiation degree and slow growth. Its main indications include: 1. primary tumors without any treatment. 2. inoperable primary tumors. 3. tumors for which the patient refuses to undergo radical surgery. 4. tumors for which important functional tissues need to be preserved or for which surgery is going to involve important organs. 5. metastatic tumor foci or isolated tumor metastases that have lost the value of surgery after surgery. 6. as a supplement to the local dose for insufficient external irradiation dose.7. .Cases of poor or failed external irradiation and/or chemotherapy.8.Prophylactic implantation to prevent local or regional spread of the tumor and to enhance the radical effect.9.Intra-operative residual tumor or cutting edge too close to the tumor (0.5cm).