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.
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.
High linear correlation (R2 > 0.8) was observed in the measured values of prostate D90%, V100%, and V150%, between the two intraoperative dosimetry approaches. The prostate D90% and V100% obtained from intraoperative dosimetry methods were in agreement with the postimplant CT dosimetry. Only the prostate V150% 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.
The results of this study have shown that both of the proposed dosimetric evaluation approaches have potential for real-time intraoperative dosimetry.
Brachytherapy. 2020 Jul 15 [Epub ahead of print]
Maryam Golshan, S Sara Mahdavi, Golnoosh Samei, Julio Lobo, Tom Pickles, W James Morris, Mira Keyes, Michael Peacock, Septimiu E Salcudean, Ingrid Spadinger
Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada; Department of Medical Physics, Vancouver Center, BC Cancer, Vancouver, British Columbia, Canada. Electronic address: ., Department of Radiation Oncology, Vancouver Center, BC Cancer, Vancouver, British Columbia, Canada., Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia, Canada., Department of Medical Physics, Vancouver Center, BC Cancer, Vancouver, British Columbia, Canada.