High dose rate (HDR) brachytherapy is a type of internal radiation therapy that delivers radiation from a radioactive pellet attached to a wire that is very briefly placed close to, or inside, the tumor(s) in the body.

Because cancer affects organs and other essential structures, it is important for radiation treatment to be tightly focused on the tumors to minimize serious side effects. This technique ensures the maximum radiation dose is given to cancerous tissues while minimizing exposure to the surrounding healthy tissue.