In vivo dosimetry and seed localization in prostate brachytherapy with permanent implants

This paper reports on the development of an interactive, intraoperative dose planning system for seed implant brachytherapy in cancer treatment. This system involves in-vivo dosimetry and the ability to determine implanted seed positions. The first stage of this project is the development of a urethral alarm probe to measure the dose along the urethra during a prostate brachytherapy treatment procedure. Ultimately the system will be used to advise the physicians upon reaching a preset dose rate or dose after total seed decay in urethra during the seed placement. The second stage is the development of a method and instrumentation for in-vivo measurements of the location of implanted seeds in the same frame as for dose planning, and using these in intraoperative treatment planning. We have developed a silicon mini-detector and preamplifier/amplifier system to satisfy the spectroscopic requirements of the urethral probe. This technique will avoid complications related to overdosing the urethra and the rectum.