Brachytherapy is also referred to as "seed therapy" or a "prostate implant." It involves the insertion of a radioactive material, commonly referred to as a source, into the body. Attempts to treat prostate cancer by placing radioactive materials into the prostate date back to the early 20th century. However, the lack of a reliable way to ensure that the radioactive materials were placed in their desired locations limited the use of brachytherapy to treat prostate cancer. In the 1980s, a technique was developed using ultrasound to guide the placement of tiny radioactive "seeds" into the prostate. This technique was first made available in the United States in the late 1980s.
There are two approaches to brachytherapy for prostate cancer: low-dose rate and high-dose rate. Prostate brachytherapy is most commonly performed using the LDR technique. With LDR brachytherapy, the seeds are permanently placed into the prostate. The radiation is given off gradually over a period of months. HDR brachytherapy involves the temporary placement of a highly radioactive source into the prostate. The radiation treatment is given off over a period of minutes and typically repeated two or three times over the course of several days. Both LDR and HDR brachytherapy may be combined with EBRT.
An ultrasound study may be performed prior to the day of the procedure to ensure there are no bones interfering with the placement of needles into the prostate. The ultrasound probe is placed into the rectum to obtain pictures of the prostate and surrounding structures. This study is commonly referred to as a transrectal ultrasound. The information obtained from the TRUS can also be used to generate a road map for seed implantation. Ultrasound imaging is typically used to define the prostate although newer approaches using CT scan or MRI may be used.