For High-Dose Rate (HDR) Brachytherapy, thin catheters or an applicator is placed in or around a tumor. These are then connected to a machine called an HDR afterloader. This machine contains a single highly radioactive iridium source at the end of a wire. The source is pushed into each of the catheters one by one under computer control. Radiation is then delivered precisely to the tumor. HDR Brachytherapy is used for prostate cancer, endometrial cancer, cervical cancer and skin cancers.