Therapeutic radiology or radiation oncology deals with radiotherapy for the control or cure of malignant tumors and proliferative diseases using high-energy ionizing radiation, megavoltage X-rays or electrons. Therapeutic radiology is a field of advanced medicine consisting of three specialties, which are clinical radiation oncology, radiation physics, and radiobiology.

Approximately one third to one half of all cancer patients have received curative or symptomatic radiotherapy. The most powerful benefit of curative radiotherapy is cancer cure and preservation of organ function or cosmesis together, which can be evident of cancers in the breast, vocal cord, head and neck, anus, limbs, brain, rectum, and non-Hodgkin's lymphoma. Sometimes, radionuclides Ir-192 or Cs-137 can be implanted in solid tumors, which is known as brachytherapy. Palliative radiotherapy is delivered to metastatic tumors in the brain, bone, lymph nodes, and other oncologic emergency conditions.

The non-cancerous benign diseases that can be cured with radiotherapy are keloids, benign tumors in the brain as pituitary adenomas, arteriovenous malformations in the brain, chroidal neovascularization, pterygium, psuedolymphoma, heterotopic ossification, and associated ophthalmopathy. Restenosis after coronary angioplasty can be prevented by intravascular brachytherapy.

The Department of Therapeutic Radiology makes every effort to increase the cancer cure rate and to improve the quality of life through basic oncologic and clinical research. The education of medical personnel is provided through lectures, and clinical and practical courses for medical students, dosimetrists, radiotherapy technologists, medical physicists, and clinical fellows.

Recently, wide-field radiotherapy has become available for total body irradiation, which is necessary in some cases of bone marrow transplantation. Radiotherapy benefits can be maximized if 3-dimensional or 4-dimensional radiotherapy can be exploited with biological achievements in treatment in the near future.