Fast dose optimization for rotating shield brachytherapy

Abstract

Purpose To provide a fast computational method, based on the proximal graph solver (POGS) – A convex optimization solver using the alternating direction method of multipliers (ADMM), for calculating an optimal treatment plan in rotating shield brachytherapy (RSBT). RSBT treatment planning has more degrees of freedom than conventional high-dose-rate brachytherapy due to the addition of emission direction, and this necessitates a fast optimization technique to enable clinical usage. Methods The multi-helix RSBT (H-RSBT) delivery technique was investigated for five representative cervical cancer patients. Treatment plans were generated for all patients using the POGS method and the commercially available solver IBM ILOG CPLEX. The rectum, bladder, sigmoid colon, high-risk clinical target volume (HR-CTV), and HR-CTV boundary were the structures included in our optimization, which applied an asymmetric dose-volume optimization with smoothness control. Dose calculation resolution was 1 × 1 × 3 mm3 for all cases. The H-RSBT applicator had 6 helices, with 33.3 mm of translation along the applicator per helical rotation and 1.7 mm spacing between dwell positions, yielding 17.5° emission angle spacing per 5 mm along the applicator. Results For each patient, HR-CTV D90, HR-CTV D100, rectum D2cc, sigmoid D2cc, and bladder D2cc matched within 1% for CPLEX and POGS methods. Also, similar EQD2 values between CPLEX and POGS methods were obtained. POGS was around 18 times faster than CPLEX. For all patients, total optimization times were 32.1–65.4 s for CPLEX and 2.1–3.9 s for POGS. Conclusions POGS reduced treatment plan optimization time approximately 18 times for RSBT with similar HR-CTV D90, organ at risk (OAR) D2cc values, and EQD2 values compared to CPLEX, which is significant progress toward clinical translation of RSBT.

Needle‐free cervical cancer treatment using helical multishield intracavitary rotating shield brachytherapy with the 169Yb Isotope

“…The HR‐CTV D 90 ( α / β = 10 Gy) values and treatment times were calculated for the HDR‐BT portion and added to the EBRT dose. Plan re‐optimization was performed using the Proximal Operator Graph Solver (POGS) for quadratic optimization, which, to ensure consistency with a commissioned clinical optimizer, was benchmarked for the IC cases to the Varian BrachyVision TPS 14 …”

Systematic Review of Intensity-Modulated Brachytherapy (IMBT): Static and Dynamic Techniques

“…Techniques were considered "dynamic" if the shield was translated or rotated during treatment relative to the source or regions of interest as part of the treatment plan. The subcategories of dynamic IMBT were "dynamic-shielded applicator" 24,25,67,69,[74][75][76][77][78][79][80] or "dynamic-shielded source," 65,66,68,[70][71][72][73] again based on whether the shield was associated with the applicator or the source. It is helpful to refer to Figure 1 throughout the following descriptions to visualize unfamiliar applicators and techniques.…”

“…Some static IMBT applicators such as DirMBT also require MBDCA-based inverse optimization. 24,[28][29][30][31]107 Pioneering investigations have been performed to improve IMBT plan quality, delivery time, and treatment-plan optimization time by improving its inverse optimization algorithm 67,75,77 or emission angleeselection algorithm. 77 A rapid emission angle selection algorithm was proposed to efficiently determine azimuthal radiation beam emission angle for RSBT approaches, presenting 19.5% to 21% improvements in high-risk clinical target volume (HR-CTV) coverage (D90) when compared with conventional approaches of exhaustive dose-volume optimization or exhaustive surface optimization.…”

“…"Dynamic" IMBT encompasses techniques in which the shield changes orientation relative to the source or tissue during treatment. Such approaches include rotating-shield brachytherapy (RSBT) [65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] and dynamic modulated brachytherapy (DMBT). 24,25 In this study, we conduct a systematic review of the IMBT literature and then analyze the investigations by disease site, technique, planning algorithm, and study type.…”

Mathematical Modelling of Dose Planning in High Dose-Rate Brachytherapy

“…Even more so if multiple radiation sources are combined in one treatment, further increasing the degrees of freedom in the dose planning problem. An optimization model for RSBT is proposed in[22]. The considered objective function is a weighted sum of two components, one being a sum of quadratic penalties for dose deviations from a prescription dose over the set of dose points, and one being a sum of the dwell time deviations in all pairs of adjacent dwell positions.…”