I125 radioactive particles is a miniature radioactive source, which is sealed with 125I diameter 0.5mm, length 3.0mm silver rod in diameter 0.8mm, length 4.5mm, wall thickness 0.05mm titanium tube connected. Continuous emission of γ-ray, half-life of 59.6 days, the effective radius of radiation is 1.7cm, the effective action time in the body for 120 days. Treatment of malignant tumor principle: tumor cell proliferation cycle: G0-G1-S-G2-M proliferation cycle, G2, M phase, a small amount of γ-ray can damage the DNA of the tumor cell nucleus, so that tumor cells lose the ability to reproduce and apoptosis. Tumor cells are more sensitive to radiation because of genetic instability, and the mechanism of repairing after being injured is incomplete. Brachytherapy destroys the DNA double strand through the direct effect of radiation or through the indirect effect of the generated free radicals, and when the tumor cells divide, they are unable to undergo cell division and die because their DNA integrity is damaged. Advantages: 1. 125I radiation particles have an effective radius of 1.7 cm for tumor treatment, and by adjusting the position of radiation particles, the overlapping radiation dose can effectively cover all of the tumor By adjusting the position of radiation particles, the overlapping radiation dose can effectively cover all the tumor and the subclinical area in the normal tissues around the tumor, achieving high radiation dose inside the tumor and rapid decay of radiation dose in the surrounding normal tissues, without increasing the radiation damage to the adjacent important tissues such as spinal cord, maximizing the killing of tumor tissues and protecting the surrounding normal tissues. 2. “The half-life of 125I radioactive particles is 60 days, which is relatively long. Long time continuous low energy x-ray and γ-ray not only destroy DNA synthesis in the nucleus of tumor cells, inhibit tumor cell mitosis and induce tumor cell apoptosis, but also make the tumor cell cycle stay in G2,M phase, which is sensitive to radiation. 125I radioactive particle implantation can be used in patients with recurrence of spinal vertebral and paravertebral tumors after external radiotherapy and surgical resection.