Radioactive Particle Targeted Implantation System (Particle Knife) is one of the most effective methods for the treatment of mid- to late-stage malignant tumors in the 21st century. Usually, “125 iodine” particles are permanently implanted into tumor tissues or into the residual cancer bed of surgically removed tumors through surgery or special radiation-protected implanters under the precise guidance of ultrasound, CT and computerized 3D stereotactic planning system. The radiation dose and the number of radioactive particles can be determined according to the size of the tumor or the residual cancer bed, so the positioning of the radioactive source is quite accurate, which is safe, effective, flexible and personalized. At present, particle therapy is mostly performed under the guidance of ultrasound and CT, which is mainly applied to the treatment of head, chest, pelvis and vertebral tumors, and can be applied to the treatment of pancreatic cancer, endometrial cancer, ovarian cancer, cervical cancer, metastatic adrenal cancer, metastatic liver cancer, primary liver cancer, prostate cancer and metastatic cancer of superficial lymph nodes throughout the body. CT-guided technology has the advantages of high localization accuracy, timely monitoring and three-dimensional spatial imaging. Compared with external irradiation, radioactive particle therapy can well realize local dose highly conformal and intensity adjustment, and through the guidance of imaging technology, it well overcomes the error caused by organ movement and has high treatment accuracy, which truly realizes the radiation therapy concept of making the dose in the tumor target area higher and the surrounding normal tissues less damaged. Dosimetric verification after radioactive particle treatment can well provide the actual irradiation dose to the tumor target area. Through postoperative evaluation, if the dose distribution in the tumor target area meets the planned requirements, the patient’s prognosis is predicted to be better, and if the dose distribution is not satisfactory, re-placement of particles or external irradiation to supplement the dose is feasible. Currently, radioactive particle therapy is the only dosimetrically validated irradiation technique in radiotherapy. The duration of radioactive particle brachytherapy is long and the dose rate of treatment is low. During continuous irradiation, tumor cell damage effects accumulate, which in turn inhibit cell proliferation. After proliferating cells are killed, cells in non-proliferating phase enter the sensitive phase and increase radiosensitivity, thus causing tumor cell death over newborn tumor cell neoplasm to destroy the tumor. For tumors that cannot be surgically removed and the application of chemotherapy and external radiotherapy is not effective, the application of minimally invasive methods to implant radioactive particles to achieve the purpose of surgical removal and preserve the function and morphology of the body can achieve a complementary effect with chemotherapy.