ESTRO 2025 - Abstract Book

S362

Brachytherapy - Physics

ESTRO 2025

4040

Digital Poster Development of a simultaneous catheter and multicriteria optimization algorithm for the Geneva applicator in HDR brachytherapy for cervical cancer Jonathan Breton-Aubé 1,2,3 , Luc Beaulieu 1,2,3 , Cédric Bélanger 4 , Sylviane Aubin 3 , Marie-Claude Lavallée 3 , Wiliam Foster 5 1 Département de physique, de génie physique et d'optique, Université Laval, Québec, Canada. 2 Centre de recherche sur le cancer, Université Laval, Québec, Canada. 3 Service de physique médicale et de radioprotection, Centre intégré de cancérologie, CHUQ, Québec, Canada. 4 Algorithm development, Elekta, Veenendaal, Netherlands. 5 Service de radio-Oncologie, Centre intégré de cancérologie, CHUQ, Québec, Canada Purpose/Objective: Complex intracavitary/interstitial (IC/IS) applicators, such as the Geneva applicator (tandem and ovoids with 6 to 14 needles; Elekta, Veenendaal, Netherlands), are commonly used for the treatment of cervical cancer with high-dose rate brachytherapy to accommodate a wide range of tumor geometries [1]. With the ongoing need for improvements in treatment, particularly in terms of dose distribution and IS catheter configurations, this study aims to validate a simultaneous sparse catheter (SC) and multicriteria (MCO) treatment planning optimization algorithm for cases treated with the Geneva applicator. Material/Methods: The proposed approach is based on two key components: first, the minimization of a multi-objective cost-function that considers the dwell times and positions of the sources; and second, a SC implementation that excludes IS catheters with minimal contribution to the total dwell time (<1%). The algorithm used for optimization of both components, gMCO, is implemented on GPU architecture, allowing the calculation of thousands of plans in a few seconds [2]. Validation is performed using a database of 15 patients treated with the Geneva applicator between 2021 and 2024 with 4 fractions of 7 Gy. For each fraction, two cases are studied: one using the clinical catheter configurations (CC+gMCO) and another where the algorithm is allowed to propose optimized catheter configurations (SC+gMCO). In both cases, 1000 plans are generated for four different values of μ, a parameter in the SC cost function that penalizes the use of IS catheters, where a larger value of μ results in fewer catheter usage. For each μ, the best plan is selected based on the optimal adherence to planning aims (soft constraints) and dose limits (hard constraints) defined in the EMBRACE II study [3]. The best plans for each case are then compared to the clinical plans (CP) in terms of IS catheter number (for each μ’s), dosimetric indices and acceptance rates.

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