HDR (high-dose radiation) brachytherapy involves the placement of several small catheters into the prostate gland. With the use of a robotic arm, a tiny, highly radioactive pellet then passes through each catheter. HDR usually consists of three radiation treatments several hours apart. Each session lasts approximately five minutes. The catheters must remain in place between each treatment. This treatment requires an overnight hospital stay and the patient must remain in bed the entire time so as not to displace the catheters.