Prostate Brachytherapy Intraoperative Dosimetry Using A Combination Of Radiographic Seed Localization With A C-Arm And Deformed Ultrasound Prostate Contours

PURPOSE: The purpose of the study was to assess the feasibility of performing intraoperative dosimetry for permanent prostate brachytherapy by combining transrectal ultrasound (TRUS) and fluoroscopy/cone beam CT [CBCT] images and accounting for the effect of prostate deformation.METHODS AND MATERIALS: 13 patients underwent TRUS and multiview two-dimensional fluoroscopic imaging partway through the implant, as well as repeat fluoroscopic imaging with the TRUS probe inserted and retracted, and finally three-dimensional CBCT imaging at the end of the implant. The locations of all the implanted seeds were obtained from the fluoroscopy/CBCT images and were registered to prostate contours delineated on the TRUS images based on a common subset of seeds identified on both image sets. Prostate contours were also deformed, using a finite-element model, to take into account the effect of the TRUS probe pressure. Prostate dosimetry parameters were obtained for fluoroscopic and CBCT-dosimetry approaches and compared with the standard-of-care Day-0 postimplant CT dosimetry.RESULTS: High linear correlation (R-2 > 0.8) was observed in the measured values of prostate D-90%, V-100%, and V-150%, between the two intraoperative dosimetry approaches. The prostate D-90% and V-100% obtained from intraoperative dosimetry methods were in agreement with the postimplant CT dosimetry. Only the prostate V(150% )was on average 4.1% (p-value <0.05) higher in the CBCT-dosimetry approach and 6.7% (p-value <0.05) higher in postimplant CT dosimetry compared with the fluoroscopic dosimetry approach. Deformation of the prostate by the ultrasound probe appeared to have a minimal effect on prostate dosimetry.CONCLUSIONS: The results of this study have shown that both of the proposed dosimetric evaluation approaches have potential for real-time intraoperative dosimetry. (C) 2020 American Brachy-therapy Society. Published by Elsevier Inc. All rights reserved.