Internal radiation therapy utilizes the natural body cavity or tissue space, or by means of intervention, to place the radioactive source in the body cavity gap adjacent to the tumor, or implant the radioactive source into the tumor site under image guidance so that the radiation can be concentrated in the tumor region. The internal radiation therapy implant can be permanent (radioactive particle implantation) and temporary (after-loading radiation therapy) according to the placement manner. Due to high targeting, the radiation intensity in the tumor region is much higher than that in normal tissues, thus achieving the purpose of effective killing of tumor cells.