1: Basic concept and scope of particle implantation therapy 1. Concept: Particle implantation is one of the contents of brachytherapy, and its basic practice is to put the enclosed radioactive source with certain specifications and activity into the human tissue directly through the minimally invasive way with the source applicator to irradiate the tumor tissue with high dose to achieve the purpose of treating tumor. Shandong Chest Hospital Tumor Center Zhang Feng 2. Particle morphology characteristics: Radioactive particle implantation can only be a broad sense of targeted therapy means, strictly speaking belongs to radiation therapy. Radionuclides such as 125I and 106pd are commonly used, with long half-life of 60 days and 17 days respectively. However, the energy of the generated r-rays is very low and the range within the tissue is 17mm, which can produce a high radiation dose locally. 125I and 106pd are sealed by high-density needle alloy tubes to form 4.8mm×0.8mm seeds, which can be implanted into the tumor with the help of surgery, ultrasound and CT guidance, and can irradiate the tumor at close range and for a long time. II. Particle implantation method: The application of ultrasound guidance, CT, MRI positioning technology fully ensures the accuracy of the implantation location, is a more ideal dose distribution in the treatment target area, and is superior to conventional treatment while improving the therapeutic effect, and has small side effects and high quality of life. The treatment complications are significantly reduced. Particle implantation is divided into temporary implantation and permanent implantation. Temporary implantation has a high activity of the radioactive source and is mostly a high-dose fractionated exposure, and most of them need to be removed by surgery again. In permanent implantation, the radioactive source activity is small and the particles are left in the tumor for a long time. Specific implantation methods: 1) template implantation; 2) ultrasound or CT guided implantation; 3) intraoperative direct implantation; 4) 3D stereotactic implantation; 5) direct implantation with the help of various scopes. The biological advantages of radioactive particle implantation therapy: 1. Tumor tissue consists of parenchymal cells (tumor cells) and mesenchymal cells (blood vessels and connective tissue). The sensitivity of tumor tissues to radiation follows the B-T law, that is, the sensitivity of human tissues to radiation is directly proportional to the reproductive capacity and inversely proportional to the degree of differentiation. The stronger the reproduction ability of the tissue, the more sensitive it is to radiation, and the lower the degree of differentiation, the more sensitive it is to radiation, and vice versa. 2.The radiosensitivity of tumor tissue is regulated by oncogene and oncogene, and the difference between it and normal tissue is expressed in value-added ability, differentiation ability, regeneration ability and tissue microvasculature. 3.Tumor cells have uncontrolled unlimited proliferation ability, but due to space limitation and insufficient vascular supply, it causes part of tumor tissues to stop proliferating and move away from vascular cell layer to become layer of lack of oxygen cells and necrotic layer, and tumors with radius more than 200um will become necrotic. The presence of oxygen-depleted cells is an important factor affecting radiosensitivity. 4.Radiation damage of cells is divided into lethal damage, sublethal damage and potentially lethal damage. The advantages of radioactive particle implantation: 1.There is a three-dimensional treatment plan design, which can accurately complete the three-dimensional morphological reconstruction of the relationship between the tumor and the surrounding tissues, and accurately design the location and quantity level of the implanted particles into the path. It meets the requirements of specific and individualized optimized design of target area dose. 2.The accepted dose of tumor target area is clearly improved, and it can achieve high dose target area fitness and reduce the complications of radiation damage. 3.Improved radiosensitivity, low dose continuous irradiation, able to irradiate tumors of different division cycles without interruption, with high radiation biological effect. 4.It can effectively protect the surrounding normal tissues. The radiation distance of radioactive particles in the tissue is short, only 1.7 cm, and the dose distribution outside the target area is well controlled by adjusting the spacing and activity of the particle source. 5.Radioactive particles are micro particles encapsulated in titanium alloy, which have good tissue compatibility with human body and will not produce radiation leakage and contamination of treatment path. 6.Simple operation, small trauma, low cost of equipment and treatment. 7.Protection safety, short half-life, low energy, low activity closed radioactive sources always have a special container placed, the surgical operation process will not be irradiated by the particles. 8, radiation complications are much lower than external radiation treatment. It solves the shortcomings of external radiation such as split irradiation, short time deficiency, uneven radiation dose due to breathing up and down movement of malignant tumor in the chest cavity and complications caused by large intensity of external radiation source. V. Treatment scope: Radioactive particles were firstly approved by FDA for the treatment of prostate cancer, and are now also clinically applied to liver cancer, lung cancer, glioma, nasopharyngeal cancer, oral cancer, rectal cancer and so on. Especially for liver cancer, lung cancer and local bone metastasis or other soft tissue metastasis, it is relatively safe and mature with good efficacy!