1.The principle of radioactive particle therapy for tumor The biological mechanism of tumor cell killing by gamma rays generated by radioactive particles is mainly high linear energy transfer (LET) rays acting directly on the DNA molecules of tumor cells to make the chain of DNA molecules single chain break, double bond break and lose reproductive ability. In the process of tumor cell growth, only a small portion of cells are continuously reproducing. In the late stage of DNA synthesis and mitotic phase in the reproductive cycle, a small amount of γ-rays can destroy the reproductive ability of tumor, and tumor cells in other stages of the reproductive cycle are less sensitive to γ-rays, and quiescent tumor cells, relatively insensitive to γ-rays. Therefore, the tumor cells can still grow rapidly in the interval between two irradiations, which directly affects the therapeutic effect of external radiotherapy. Although the energy of γ-rays produced by implanting radioactive particles between tumor tissues is not large, it can continuously act on tumor cells, so it can continuously kill tumor stem cells, and after sufficient dose and half-life, it can make all tumor cells lose their reproduction ability, so as to achieve a more complete therapeutic effect. 2.What are the biological advantages of radioactive particles for tumor treatment? The duration of radioactive particle brachytherapy is long and the dose rate of treatment is low. During the continuous irradiation, the tumor cell damage effect accumulates, which in turn inhibits cell proliferation. After the proliferating cells are killed, the cells in non-proliferating enter the sensitive phase and increase the radiosensitivity, thus causing the tumor cells to die over the newborn tumor cells to destroy the tumor. 3.What are the special advantages of radioactive particles for tumor treatment? (1) Complementary effect with surgery: Surgery with implantation of radioactive particles is the most common way of treatment, and its greatest effect is the overall killing of tumor. (2) Improve the completeness of tumor cure: When the tumor infiltrates the adjacent important organs, even if the tumor can be removed, it is only a palliative surgery and the prognosis is very poor. In addition, radioactive particle implantation is used during surgery to implant particles in lymphatic channels, residual tumor tissues and bordering parts of tumor, which is expected to obtain complete cure effect. (3) Reduce surgical trauma, shorten operation time and reduce postoperative complications: intraoperative puncture technique of radioactive particle implantation causes minimal trauma to normal tissues, eliminates the need to fully reveal the surgical field and avoid blind extensive fat-clearing operation, which can reduce surgical trauma and interference with normal tissues to a greater extent, and the patient’s postoperative recovery is smooth. In the palliative resection of tumor, the implantation of radioactive particles by puncture technique is simple and does not need to worry about the residual size of tumor, which greatly reduces the degree of accidental injury to normal tissues, the incidence of postoperative complications is reduced accordingly, and the difficulty of postoperative care and workload of patients are reduced. (4) For tumors that cannot be removed surgically and the effects of chemotherapy and external radiotherapy are not effective, the implantation of radioactive particles by minimally invasive methods can achieve the purpose of surgical removal. (5) The effect of preserving the function and morphology of the body. (6) Complementary effect with chemotherapy. 4.What is the difference between radioactive particle therapy and traditional external radiotherapy? The advantages of “particle knife” compared with traditional external radiotherapy are (1) Although external radiotherapy equipment is progressing rapidly, the treatment of intrathoracic malignant tumors moving up and down by breathing still has the defect of uneven radiation dose, and the intensity of its radiation source is too large, which causes more obvious complications to the patient’s organism; whereas The particles of “particle knife” are directly planted in the tumor, and the radiation dose is uniform and not affected by the activity, and it rarely damages the normal tissues. (2) External radiotherapy cannot avoid the shortcomings of fractional short-time. External radiotherapy can only treat cells in one part of the tumor reproduction cycle. After the end of irradiation, the tumor cells in other phases can still recover their reproduction ability soon. The tumor cells can be stimulated by any stimulation to change from quiescent cells to active cells, and the cell multiplication time is significantly shortened, so they can still grow rapidly in the interval between irradiation sessions, which directly affects the therapeutic effect of external radiotherapy. In contrast, the particles of “particle knife” can irradiate tumor cells in the tumor for up to 180 days, until all tumor cells are killed. 5.What are the tumors that are suitable for radioactive particles? Particle Knife can treat solid tumors in all parts of the body, and the indications include: (1) Untreated primary tumors, such as prostate cancer, lung cancer, etc. (2) Tumors that require preservation of important functional tissues, or where surgery would involve important organs, such as deep brain tumors. (3) Cases in which patients are unwilling to undergo radical resection, such as thyroid cancer, endometrial cancer, tongue cancer, etc. (4) Prophylactic implantation during surgery to prevent local spread or regional spread of tumor and enhance radical effect. (5) Metastatic tumor lesions or postoperative isolated tumor metastases that lose their surgical value, such as multiple metastatic tumors of the lung. (6) Inoperable primary cases, such as giant hepatocellular carcinoma, lung cancer, nasopharyngeal carcinoma, etc. (7) Tumor infiltrating important organs that cannot be completely removed. (8) Cases with poor or failed effect of external irradiation, etc. (9) Chemotherapy-resistant patients.