Intraoperative planning and evaluation of permanent prostate brachytherapy: report of the American Brachytherapy Society.

PURPOSE: The preplanned technique used for permanent prostate brachytherapy has limitations that may be overcome by intraoperative planning. The goal of the American Brachytherapy Society (ABS) project was to assess the current intraoperative planning process and explore the potential for improvement in intraoperative treatment planning (ITP). METHODS AND MATERIALS: Members of the ABS with expertise in ITP performed a literature review, reviewed their clinical experience with ITP, and explored the potential for improving the technique. RESULTS: The ABS proposes the following terminology in regard to prostate planning process: *Preplanning--Creation of a plan a few days or weeks before the implant procedure. *Intraoperative planning--Treatment planning in the operating room (OR): the patient and transrectal ultrasound probe are not moved between the volume study and the seed insertion procedure. * Intraoperative preplanning--Creation of a plan in the OR just before the implant procedure, with immediate execution of the plan. *Interactive planning--Stepwise refinement of the treatment plan using computerized dose calculations derived from image-based needle position feedback. *Dynamic dose calculation--Constant updating of dose distribution calculations using continuous deposited seed position feedback. Both intraoperative preplanning and interactive planning are currently feasible and commercially available and may help to overcome many of the limitations of the preplanning technique. Dosimetric feedback based on imaged needle positions can be used to modify the ITP. However, the dynamic changes in prostate size and shape and in seed position that occur during the implant are not yet quantifiable with current technology, and ITP does not obviate the need for postimplant dosimetric analysis. The major current limitation of ITP is the inability to localize the seeds in relation to the prostate. Dynamic dose calculation can become a reality once these issues are solved. Future advances can be expected in methods of enhancing seed identification, in imaging techniques, and in the development of better source delivery systems. Additionally, ITP should be correlated with outcome studies, using dosimetric, toxicity, and efficacy endpoints. CONCLUSION: ITP addresses many of the limitations of current permanent prostate brachytherapy and has some advantages over the preplanned technique. Further technologic advancement will be needed to achieve dynamic real-time calculation of dose distribution from implanted sources, with constant updating to allow modification of subsequent seed placement and consistent, ideal dose distribution within the target volume.

The American Brachytherapy Society recommendations for permanent prostate brachytherapy postimplant dosimetric analysis.

PURPOSE: The purpose of this report is to establish guidelines for postimplant dosimetric analysis of permanent prostate brachytherapy. METHODS: Members of the American Brachytherapy Society (ABS) with expertise in prostate dosimetry evaluation performed a literature review and supplemented with their clinical experience formulated guidelines for performing and analyzing postimplant dosimetry of permanent prostate brachytherapy. RESULTS: The ABS recommends that postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy for optimal patient care. At present, computed tomography (CT)-based dosimetry is recommended, based on availability cost and the ability to image the prostate as well as the seeds. Additional plane radiographs should be obtained to verify the seed count. Until the ideal postoperative interval for CT scanning has been determined, each center should perform dosimetric evaluation of prostate implants at a consistent postoperative interval. This interval should be reported. Isodose displays should be obtained at 50%, 80%, 90%, 100%, 150%, and 200% of the prescription dose and displayed on multiple cross-sectional images of the prostate. A dose-volume histogram (DVH) of the prostate should be performed and the D90 (dose to 90% of the prostate gland) reported by all centers. Additionally, the D80, D100, the fractional V80, V90, V100, V150 and V200 (i.e., the percentage of prostate volume receiving 80%, 90%, 100%, 150%, and 200% of the prescribed dose, respectively), the rectal, and urethral doses should be reported and ultimately correlated with clinical outcome in the research environment. On-line real-time dosimetry, the effects of dose heterogeneity, and the effects of tissue heterogeneity need further investigation. CONCLUSION: It is essential that postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy. Guidelines were established for the performance and analysis of such dosimetry.