(Thursday, 7/16/2020) 10:30 AM - 11:30 AM [Eastern Time (GMT-4)]
Room: Track 3
Purpose: catheter position selection critically affects the quality of treatment plans in prostate cancer high-dose-rate (HDR) brachytherapy. The current standard approach selects needles based on human intuition and a plan is generated based on inserted needle positions. Such a two-stage planning process is not only time-consuming but cannot ensure plan optimality, leading the selection of unnecessary needles and injury to patients. In this study, we proposed a method to simultaneously select needle positions and determine dwell time.
Methods: formulated the needle selection problem and inverse dwell time optimization problem in a unified framework. In addition to the dose objectives of the planning target volume (PTV) and organs at risk (OARs), the objective function incorporated a group-sparsity term with a needle-specific adaptive weighting scheme, in order to generate high-quality plans with the minimal number of needles. The optimization problem was solved by a fast iterative shrinkage-thresholding algorithm, yielding selected needle positions and dwell times of the dwell positions in these selected needles. For validation purposes, we tested the proposed algorithm on five patient cases previously treated at our institution.
Results: to the plan optimized with manually selected needles, the proposed algorithm was able to improve the PTV coverage by increasing V100 by ~2% and reducing V125, V150, and V200 by ~13%, with similar dose to OARs: D1cc for urethra and bladder were reduced by 2.64 Gy and 0.07 Gy, while D1cc for rectum was slightly increased by 0.24 Gy. On average, the number of selected needles was reduced by two. The computational time solving the proposed algorithm was ~15 seconds.
Conclusion: proposed a novel inverse planning algorithm for prostate HDR brachytherapy to perform needle selection and dwell time optimization simultaneously. Tests in real patient cases demonstrated its effectiveness.
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