A fast multitarget inverse treatment planning strategy optimizing dosimetric measures for high‐dose‐rate (HDR) brachytherapy

Abstract

Purpose: In this study, we introduce a novel, fast, inverse treatment planning strategy for interstitial high-dose-rate (HDR) brachytherapy with multiple regions of interest solely based on dose-volumehistogram-related dosimetric measures (DMs). Methods: We present a new problem formulation of the objective function that approximates the indicator variables of the standard DM optimization problem with a smooth logistic function. This problem is optimized by standard gradient-based methods. The proposed approach is then compared against state-of-the-art optimization strategies. Results: All generated plans fulfilled prescribed DMs for all organs at risk. Compared to clinical practice, a statistically significant improvement ðp ¼ 0:01Þ in coverage of target structures was achieved. Simultaneously, DMs representing high-dose regions were significantly reduced ðp ¼ 0:01Þ. The novel optimization strategies run-time was (0.8 AE 0.3) s and thus outperformed the best competing strategies of the state of the art. In addition, the novel DM-based approach was associated with a statistically significant ðp ¼ 0:01Þ increase in the number of active dwell positions and a decrease in the maximum dwell time. Conclusions:The generated plans showed a clinically significant increase in target coverage with fewer hot spots, with an optimization time approximately three orders of magnitude shorter than manual optimization currently used in clinical practice. As optimization is solely based on DMs, intuitive, interactive, real-time treatment planning, which motivated the adoption of manual optimization in our clinic, is possible.

An extended dose–volume model in high dose‐rate brachytherapy – Using mean‐tail‐dose to reduce tumor underdosage

“…(Heuristics are algorithms with no guarantees of finding an optimal solution and no information about the quality of an optimal solution, but which in practice often are able to quickly find good solutions.) The DVM formulation developed by Guthier et al . approximated the Heaviside functions with smooth, nonconvex functions and find good solutions in short solution times (a few seconds).…”

“…The DIs are in clinical practice mainly used in the evaluation of dose plans and DVMs are not commonly used in clinically available treatment planning software. The DVMs have, however, been shown to produce dose plans which are clinically acceptable . Reference includes the opinion from an expert on the dose plans, and Ref.…”

“…Reference includes the opinion from an expert on the dose plans, and Ref. compares dose plans from a number of optimization models, including models based on dose–volume criteria, with dose plans from manual planning.…”

“…The above‐mentioned weaknesses of current methods have resulted in a research focus on finding improved automated methods for dwell time optimization, capable of using the dosimetric indices (or an approximation thereof) as the actual quality measures for the optimization . While the advantage of using the dosimetric indices as quality measures is obvious (due to the clinical guidelines), it is important to be aware of the pitfalls and weaknesses of this approach, which can be severe if not foreseen.…”

“…The aim of this work is first to develop an improved and safer DVH‐based optimization model for dose planning. Our starting‐point is published DVH‐based models that have been evaluated positively against clinical dose plans . However, our work offers no comparison with such plans but focuses solely on the extension of the model.…”