Real time intraoperative evaluation of implant quality and dose correction during prostate brachytherapy consistently improves target coverage using a novel image fusion and optimization program

Publication date: Available online 20 January 2017
Source:Practical Radiation Oncology
Author(s): Michael J. Zelefsky, Gilad N. Cohen, Amandeep S. Taggar, Marisa Kollmeier, Sean McBride, Gig Mageras, Marco Zaider
PurposeTo describe the process and outcome of performing postimplantation dosimetric assessment and intraoperative dose correction during prostate brachytherapy using a novel image fusion–based treatment-planning program.Materials and MethodsTwenty-six consecutive patients underwent intraoperative real-time corrections of their dose distributions at the end of their permanent seed interstitial procedures. After intraoperatively planned seeds were implanted and while the patient remained in the lithotomy position, a cone-beam computed tomography scan was obtained to assess adequacy of the prescription dose coverage. The implanted seed positions were automatically segmented from the cone-beam images, fused onto a new set of acquired ultrasound images, and re-imported into the planning system and re-contoured. Dose distributions were re-calculated based upon actual implanted seed coordinates and re-contoured ultrasound images and reviewed. If any dose deficiencies within the prostate target were identified, additional needles and seeds were added. Once an implant was deemed acceptable, the procedure was completed and anesthesia was reversed.ResultsWhen the intraoperative ultrasound–based quality assurance assessment was performed after seed placement, the median V100 was 93% [range, 74% to 98%]. Prior to seed correction, 23% (6/26) of cases were noted to have V100<90%. Based on this intraoperative assessment and re-planning, additional seeds based on the re-plan were placed into dose-deficient regions within the target to improve target dose distributions. Post-correction, the median V100 was 97% [range, 93% to 99%]. Following intraoperative dose corrections, all implants achieved V100>90%.ConclusionsIn these patients, postimplantation evaluation during the actual prostate seed implant procedure was successfully applied to determine the need for additional seeds to correct dose deficiencies prior to anesthesia reversal. When applied, this approach should significantly reduce intraoperative errors and chances for suboptimal dose delivery during prostate brachytherapy.



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