Radiation therapy refers to the treatment of cancer tumors with radionuclide rays, ordinary X-rays from X-ray therapy machines, high-energy X-rays from gas pedals, and electron beams, protons, fast neutrons, negative wood mesons, and other heavy particles from various gas pedals. Radiation therapy in a broad sense includes both radiation therapy for tumors in radiotherapy departments and internal radionuclide therapy in nuclear medicine departments (e.g. 131I for thyroid cancer and hyperthyroidism, 32P for cancerous pleural fluid, etc.). Radiation therapy in a narrow sense generally refers to the former only, i.e. what people generally call tumor radiation therapy. There are two types of radiation therapy: one is long-distance radiation therapy (external radiation), which means that the radiation source is irradiated at a certain distance from the patient’s body, and the radiation penetrates from the patient’s body surface to a certain depth in the human body to achieve the purpose of tumor treatment, which is the most widely used and the most important; the other is brachytherapy (internal radiation), which means that the radiation source is sealed inside the tumor or on the surface of the tumor, such as into the natural cavity of the human body or inside the tissues (such as the natural cavity). The other is brachytherapy (internal irradiation), in which the radiation source is sealed inside the tumor or on the surface of the tumor, such as into the natural cavity or tissues of the body (such as the tongue, nose, pharynx, esophagus, trachea and uterine body).