125I radioactive particles, also known as particle knife, is a new tumor treatment method that complements the shortcomings of surgery and external radiotherapy in the international medical community. The main feature is that 125I radioactive particles can be permanently buried in the tumor body, sub-tumor areas and lymphatic pathways that may metastasize for continuous treatment, or the 125I radioactive particles can be placed in the tumor under the surveillance of ultrasound or CT with the application of minimally invasive technology to provide lasting radiation treatment. It has the advantages of small trauma, accurate targeting, low dose continuous gamma radiation irradiation and no pollution, which meets the environmental protection standard. The local tumor control rate can reach over 90%. 125I particle is an extremely advanced miniature sealed radioactive source. It is composed of a silver rod, adsorbed with the isotope iodine 125 and a titanium alloy shell, with a total length of 4.5 mm, cylindrical shape and a diameter of 0.8 mm. 125I particles release energy of 27.4-31.4 KEV of X-rays and 35.5 KEV of gamma rays, with a half-life of 60.1 days and a full-life of 400 days. In the mid-1980s, 125I intra-tissue radiotherapy for cancer treatment was widely used in Europe, the United States and Australia, etc. After years of clinical application results, it was found that 125I particles can be applied to all solid tumors except for leukemia (blood cancer). It has obvious efficacy on prostate cancer, head and neck cancer, lung cancer, liver cancer, pancreatic cancer and soft tissue malignant tumors, and it has greatly improved the quality of life for patients after treatment. Iodine 125 internal radiotherapy has now been used as the preferred modality for cancer treatment in many foreign cancer fields.