Another form of brachytherapy is High Dose Rate (HDR) Brachytherapy. Unlike LDR brachytherapy which is used for low risk prostate cancer, HDR brachytherapy is usually employed in conjunction with external beam radiation where the tumour characteristics suggest an intermediate or high risk prostate cancer.At this point in time HDR brachytherapy is used in combination with external beam radiotherapy, and not as a stand alone treatment like seed brachytherapy.
The treatment is delivered through the use of small malleable hollow metallic catheters inserted directly into the prostate gland. These metallic catheters act as a conduit allowing a radiation source to be placed within the prostate. Three radiation treatments can then be delivered through these catheters. Once the radiation has been delivered, the catheters are removed (typically the next day) and no radioactive material is left within the prostate gland. A computer controlled device, called a Remote Afterloader, moves a radioactive iridium source, located on the end of a wire, into each of the catheters. The radioactive iridium source is then positioned at a number of “dwell” positions to deliver the radiation dose within the prostate. These positions are determined with the aid of a planning computer allowing optimal dose of radiation to the prostate. The treatment is tailored to deliver an optimal dose to the prostate and to minimize the dose to other structures, including the urethra and the rectum. The ability to alter the dose after the plastic catheters have been inserted into the prostate is one of the major advantages of HDR brachytherapy.