ESTRO 2025 - Abstract Book

S3701

Physics - Quality assurance and auditing

ESTRO 2025

(2) Baeza JA, Wolfs CJA, Nijsten SMJJG, Verhaegen F. Validation and uncertainty analysis of a pre-treatment 2D dose prediction model. Phys Med Biol. 2018;63(3). (3) Van Elmpt WJC, Nijsten SMJJG, Schiffeleers RFH, Dekker ALAJ, Mijnheer BJ, Lambin P, et al. A Monte Carlo based three-dimensional dose reconstruction method derived from portal dose images. Med Phys. 2006;33(7):2426–34.

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Poster Discussion Development of a platform to assess the quality of radiotherapy plans Tiago Ventura 1 , Rafael Lobão 2 , Tania Santos 1 , Josefina Mateus 1 , Maria do Carmo Lopes 1 1 Medical Physics, IPO Coimbra, Coimbra, Portugal. 2 Radiotherapy, University Hospital Erlangen, Erlangen, Germany Purpose/Objective: The quality of radiotherapy plans can be assessed by evaluating their dosimetric performance, which includes the clinical appropriateness of the dose distribution, as well as their complexity and robustness. In this context, this work aimed to develop a platform, called qualComp, to characterise the dosimetric performance and complexity of radiotherapy plans. Material/Methods: The qualComp platform is organised in three modules: Import, Calculation, and Search and Display. The first module organises and processes patient files according to the AAPM TG-263 nomenclature. Dosimetric performance is assessed in the Calculation module through an enhanced configuration of SPIDERPlan, which integrates dosimetric indices such as CI, COIN, GI, and supports statistical analyses by plan groups. Plan complexity metrics tailored to Halcyon and Tomotherapy linacs have also been implemented. The Search and Display module includes automatic DVH reading and SPIDERplan template configuration tools, and also a solution for visualising CT, images, structures and dose distributions. The performance of qualComp was tested for prostate pathology in a longitudinal study of 578 VMAT plans for Halcyon optimised with Eclipse TPS between May 2021 and May 2024. Plans were divided into three time periods: (1) before implementation of local planning protocol (May 2021 - April 2022), (2) during protocol implementation (May 2022 - April 2023) and (3) after stabilisation of the planning learning curve (May 2023 - May 2024). Dosimetric performance was evaluated by configuring SPIDERplan for prostate pathology according to the radiation oncologist clinical preferences and the institutional protocol for prescribing and organ-at-risk tolerance criteria, while twelve complexity metrics were also assessed. Results: The qualComp platform successfully automated the evaluation of dosimetric performance and complexity for prostate plans. Dosimetric performance, represented by the SPIDERplan global score, showed no statistically significant difference between the first (0.404) and third periods (0.399, p-value > 0.05, Welch's t-test). For plan complexity statistically significant differences (p-value < 0.05 for Welch t-test) were found for 10 of the 12 metrics, demonstrating a systematic reduction in complexity. Conclusion: qualComp is an effective tool for evaluating the quality of radiotherapy treatment plans, enabling the automated assessment of individual plans and cohort trends. The quality assessment of the plans showed that the complexity of the plans was progressively reduced without affecting their dosimetric performance, as a result of the introduction into clinical practice of a protocol of recommendations for planning in VMAT, aimed at harmonising planning approaches among local planners.

Keywords: Plan quality, complexity, dosimetric perfomance