Improvement of transperineal implant dosimetry by intraoperative cystoscopic confirmation of prostate anatomy

Purpose: A simple, inexpensive method to aid in the accurate placement of p ermanent seeds for prostate brachytherapy is described. The effect of ident ifying the prostate base and apex cystoscopically relative to registration seeds placed at the beginning of the implant is discussed. Materials and Methods: At the beginning of each implant procedure a pair of marker seeds are first placed in the prostate, including 1 seed at the bas e and 1 at the apex. Using a cystoscope, the urologist identifies the prost atic base and apex, and a fluoroscopic record is obtained. The positions of the base and apex relative to the marker seeds are monitored throughout th e case via fluoroscopy to aid in needle and seed placement for the implant. Results: Use of this method significantly improved coverage of the prostate apex, reduced overall dose variance in the prostate base and improved over all gland dosimetry by 22% as measured by the D90 quality metric (minimal d ose which covers 90% of the prostate volume). Conclusions: While the clinical efficacy of improved target coverage on loc al control and survival awaits further clinical investigation, we encourage others to adopt this easy technique to ensure better, more consistent inte rstitial implants.