The Department of Radiation Oncology, which is called the Therapeutic Radiology Department, is responsible for radiation therapy. Radiation therapy is one of the three major cancer treatments, along with surgery and chemotherapy, as a method of clinical medicine. The radiation used for radiation therapy has a very short wavelength and high energy. Radiation to the human body causes denaturation of the nucleic acid and kills tumor cells. Adjacent normal cells may also be affected, but in recent years the development of equipment has allowed them to irradiate a sufficient amount of radiation without damaging normal cells. It treats malignant tumors, mainly cancer, but also benign tumors and some benign diseases. Radiation oncology differs slightly from other departments that use radiation. In the Department of Radiology, non - radiation such as low - energy radiation or ultrasound is used to acquire image information and help diagnosis. Radiation oncology is treated with high - energy radiation. In the Department of Nuclear Medicine, which uses radioactive isotopes, it is responsible for inspection, imaging, and treatment using an open source exposed to a radioactive source. In the Department of Radiation Oncology, the radiation source is sealed with other materials (mainly various high-density metals) And a sealed source that is not exposed to the outside is used mainly.