ESTRO 2025 - Abstract Book

S3668

Physics - Quality assurance and auditing

ESTRO 2025

Conclusion: A pilot multicentre audit designed to address the consistency of dosimetric properties between 3D printed objects has been completed. Results indicate the achievable geometric and dosimetric accuracy, which can inform QA tolerances. A myriad of variables can affect the properties of 3D printed objects, so regular QA and optimisation of local printing parameters is important. This work suggests that a knowledge of 3D printing capability across different systems can help centres to minimise variability in their prints.

Keywords: 3D Printing, Audit, Radiotherapy

3419

Digital Poster Smarter commissioning and less QA: bridging the gap between treatment plan complexity and dose calculation accuracy

Daan Hoffmans, Nicky van Lobenstein, Yvonne van Herten, Arjan Bel, Duncan den Boer Radiation Oncology, Amsterdam University Medical Center, Amsterdam, Netherlands

Purpose/Objective: The use of complexity metrics has been proposed as a method to preselect treatment plans that qualify for measurement-based patient specific QA, as an alternative to an independent dose calculation. However, predicting measurement results based on plan complexity is found to be challenging 1 . The aim of this study is to define a commissioned space of plan complexity that is formed based on asynchronous sliding gap plans which are sensitive to the modelling of the leaf shape in the treatment planning system 2 . Such a method could be used to optimize the balance between clinical plan complexity and parameter tuning of the treatment planning system. Material/Methods: A total of 30 asynchronous sliding gap fields were generated (Figure 1) and the dose in the isocenter was calculated at a depth of 5 cm using Eclipse (V16.1, Varian a Siemens Healthineers Company). Using a farmer type ionization chamber, we measured the delivered dose in identical geometry. Both calculated and measured dose were normalized against a calculated and measured 10x10 cm 2 field. For these sliding gap fields, we calculated the Aperture irregularity, Edge Metric, Mean Field Area and Circumference Per Area 1,3 using in-house developed software (Matlab, R2021a, Mathworks). For visualization, we calculated the principal components of these metrics (RStudio, v2023.06.1).