The “particles” of “particle knife” are also called “sealed seed source”, although the volume of each “particle” is smaller than a grain of rice. Although each “particle” is smaller than a grain of rice, its role cannot be underestimated, as it contains 125 iodine, a radioactive substance that has the effect of killing tumor cells. Doctors use a set of special instruments to place the radioactive particles directly into the tumor like “mine-laying”. Each particle in the body is like a small sun, continuously producing rays to irradiate the surrounding tumor tissue. The gamma rays emitted by 125 iodine can kill tumor cells, thus achieving the same effect as removing a tumor with a scalpel, which is why it is also called “particle knife”. This is a minimally invasive technique supported by imaging technology, which can achieve high dose of radiation in the target area of the tumor and no dose in the surrounding tissues, and is effective for localized progressive tumors that are inoperable. 125 iodine particle therapy for malignant tumors is a new technology developed in recent years, which is rapidly carried out worldwide because of less damage to normal tissues and better efficacy. 1.Why use radioactive 125 iodine particles? Radioactive 125 iodine particles have 4 characteristics: Firstly, its radiation energy is low, which has no damage to the surrounding healthy tissues. The second is that the irradiation distance is short, only 1.7 cm, which is not harmful to doctors and families. Thirdly, it can continue to kill tumor cells every second for 24 hours without stopping. The fourth is the long duration of particle action, up to 180 days. Moreover, 125 iodine particles are currently social security category B drugs, and the national medical insurance will bear most of the treatment cost. 2.What are the advantages of “particle knife” compared with traditional external radiotherapy? (1) Although the external radiotherapy equipment is progressing rapidly, the treatment of intrathoracic malignant tumors that move 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 body; while the particles of “particle knife” are directly planted in the tumor, which is not affected by the activity and rarely (2) External radiotherapy cannot avoid the complications of the patient’s body. (2) External radiotherapy cannot avoid the shortcomings of “fractionated short time”. External radiotherapy usually irradiates 5 days a week for more than 10 seconds a day, and this kind of fractional short-time irradiation can only have a therapeutic effect on cells in part of the tumor reproduction cycle. After the irradiation is over, the tumor cells in other phases can still recover their reproductive ability soon. Therefore, the tumor cells 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 continuously irradiate the tumor cells for up to 180 days in the tumor, which can kill all the tumor cells. (3) The rays of external radiotherapy come from outside the body, and the rays must pass through the important structures of skin, muscle and internal organs to reach the tumor tissue. While the tumor is irradiated by the rays, the normal tissues are also irradiated. It is possible that before the tumor cells are killed, the normal tissues are already severely damaged by radiation, leading to serious complications. In contrast, in theory, the particles can be evenly distributed in the tumor, which can achieve a high radiation dose in the tumor, while the surrounding normal tissues are not irradiated, achieving the effect of reducing the complications of radiation therapy. 3.How to perform particle implantation therapy? Most of the particle implantation treatments are performed through skin puncture under CT or ultrasound guidance, and local anesthesia is sufficient to keep the patient awake during the whole process. The procedure usually takes 1-3 hours, and a tumor usually requires 1-2 implantations. The patient is reviewed 1-3 months after surgery, and some patients may need to be replanted with particles. Particle implantation is also performed intraoperatively or under lumpectomy. 4.How long do the implanted particles work? After the radioactive particles are implanted into the tumor, they start to release gamma rays continuously to kill the tumor cells, and the effective killing time is 180 days. 5.When is the most obvious effect? The most obvious effect is in the first and second month after the radioactive particle implantation. 70% or more of the tumors can be reduced by more than half, and about 30% can disappear completely. Six months after the operation is the best time to evaluate the implantation of particles. 6.What happens when the implanted particles fail? The shell of radioactive 125 iodine particles is made of titanium alloy, which is highly compatible with human body and can exist in the body permanently without causing rejection.