Abstract
PurposeBi‐objective simultaneous optimization of catheter positions and dwell times for high‐dose‐rate (HDR) prostate brachytherapy, based directly on dose‐volume indices, has shown promising results. However, optimization with the state‐of‐the‐art evolutionary algorithm MO‐RV‐GOMEA so far required several hours of runtime, and resulting catheter positions were not always clinically feasible. The aim of this study is to extend the optimization model and apply GPU parallelization to achieve clinically acceptable computation times. The resulting optimization procedure is compared with a previously introduced method based solely on geometric criteria, the adapted Centroidal Voronoi Tessellations (CVT) algorithm.MethodsBi‐objective simultaneous optimization was performed with a GPU‐parallelized version of MO‐RV‐GOMEA. This optimization of catheter positions and dwell times was retrospectively applied to the data of 26 patients previously treated with HDR prostate brachytherapy for 8–16 catheters (steps of 2). Optimization of catheter positions using CVT was performed in seconds, after which optimization of only the dwell times using MO‐RV‐GOMEA was performed in 1 min.ResultsSimultaneous optimization of catheter positions and dwell times using MO‐RV‐GOMEA was performed in 5 min. For 16 down to 8 catheters (steps of 2), MO‐RV‐GOMEA found plans satisfying the planning‐aims for 20, 20, 18, 14, and 11 out of the 26 patients, respectively. CVT achieved this for 19, 17, 13, 9, and 2 patients, respectively. The P‐value for the difference between MO‐RV‐GOMEA and CVT was 0.023 for 16 catheters, 0.005 for 14 catheters, and <0.001 for 12, 10, and 8 catheters.ConclusionsWith bi‐objective simultaneous optimization on a GPU, high‐quality catheter positions can now be obtained within 5 min, which is clinically acceptable, but slower than CVT. For 16 catheters, the difference between MO‐RV‐GOMEA and CVT is clinically irrelevant. For 14 catheters and less, MO‐RV‐GOMEA outperforms CVT in finding plans satisfying all planning‐aims.
Highlights
Treatment planning for high-dose-rate (HDR) prostate brachytherapy consists of two parts
We have previously shown that when optimizing catheter positions based on the clinical protocol, a constraint is necessary to restrict dose to healthy tissue outside of delineated targets and organs at risk (OARs),[21] especially since dwell positions outside of the prostate can be used for dose planning
For 16 catheters, GOMEA was able to find treatment plans satisfying all planning-aims for 20 out of the 26 patients, and the front came within 1% of the Golden Corner for two other patients
Summary
Treatment planning for high-dose-rate (HDR) prostate brachytherapy consists of two parts. There is an intuitive key trade-off in a given clinical protocol between the planning-aims for the targets (i.e., prostate and seminal vesicles should receive enough dose) and those for OARs (i.e., bladder, rectum, and urethra should not receive too much dose). This can be captured by using two objectives, i.e., a bi-objective approach. Optimization does not result in a single treatment plan, but in a set of plans, each of which has a different trade-off between the two objectives. The physician can choose a plan from this front, potentially using additional patient information such as age and previous treatments
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