Program Information
An Interactive Intra-Operative Inverse Treatment Planning System for Image Guided Interstitial Brachytherapy
C Guthier1*, A Visvanathan2 , R Cormack3 , (1) Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, and Harvard Medical School, Boston, Ma, (2) Department of Radiation Oncology and Molecular Radiation Sciences, John Hopkins Medicine, Baltimore, MD, (3)
Presentations
WE-AB-605-2 (Wednesday, August 2, 2017) 7:30 AM - 9:30 AM Room: 605
Purpose: Interstitial high-dose-rate brachytherapy (iHDR-BT) is a treatment modality for gynecologic cancers. Image-guided needle placement may benefit from real-time dosimetric evaluation of implant quality. This study presents an interactive inverse treatment planning system (I-ITP) for image-guided iHDR-BT. The guidance provided enables catheter optimization and plan adaption using real-time catheter tracking.
Methods: As part of an IRB-approved study plan structures, template orientation and needle trajectories of 20 patients were extracted from the medical record. Deviations from ideal catheter trajectories were used as simulated needle trajectory measurement. After an initial plan {S0}, is generated two strategies are compared; either catheters are inserted followed by a catheter reconstruction and plan-evaluation and if necessary re-optimization {S1}, or an iterative approach where dwell-times and configuration of remaining catheters are re-optimized after each implanted catheter {S2}. Further we opted for a catheter reduction of 25% with respect to the applied plan for S0. For each strategy, the dosimetric performance and optimization time is compared to the original clinical plan {OCP}.
Results: All plans fulfilled the defined dosimetric goals for OARs. The mean D90 of the CTV was OCP:(111.4±12.4)%, S1:(112.4±9.3)% , and S2:(112.8±9.6)%. For the vagina the D100 was found to be OCP:(54.2±13.5)%, S1:(57.1±11.5)%, and S2:(57.0±13.0)%. Based on a Wilcoxon signed-rank test the metrics for both targets and scenarios do not show a statistically significant difference to the OCPs (p>.05). The optimization time was S0:(5.7±3.8)s, S1:(1.9±1.6)s, S2:(8.5±8.4), and for OCP approximately 20-30 minutes.
Conclusion: The proposed I-ITP system demonstrates real-time dosimetric guidance in a clinically relevant timeframe. The proposed workflow proves that I-ITP has the potential to reduce the number of used catheters which results in less trauma and less implantation time. A reduction in planning and implantation time also reduces the time in the operating room and the time a patient is under anesthesia.
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