There is a type of radiation therapy that irradiates through human tissue to the tumor to kill the internal tumor, called external radiation. The process of external radiation reaching the tumor through the human body also causes some damage to the normal tissues of the human body, resulting in certain complications. Now there is a kind of radioactive element iodine-125 particle, which is put in a silver rod and enclosed with titanium alloy metal on the outside to make a very small metal rod, and put the metal rod inside the tumor, the range is very short, the effect is only to kill the tumor cells, there is basically no damage to the surrounding normal tissue. Iodine-125 particles are radioactive elements, which are strictly controlled by the state, and because the outside is wrapped with metal, it will not leak, so it is a kind of green radioactive energy.