ESTRO 2024 - Abstract Book

S3243

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

1. Esipova TV. et al, Anal. Chem. 2011; 83, 22, 8756–8765

2. Kanouta E. et al, Med Phys. 2023; 50: 2450–2462

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Digital Poster

EPID pre-treatment PSQA with SunCheck PerFRACTION: a single center comparison with ArcCheck

Stefania Linsalata 1 , Odette Akouvi Satsi 2 , Patrizio Barca 1 , Antonio Claudio Traino 1

1 Azienda Ospedaliero Universitaria Pisana, Medical Physics Unit, Pisa, Italy. 2 International Center for Theoretical Physics, Master of Advanced Studies in Medical Physics, Trieste, Italy

Purpose/Objective:

Patient Specific Quality Assurance (PSQA) is a laborious task for the medical physics workload, but it is still advisable also from the international regulations (e.g., European Union 2013/59/EURATOM), especially for very complex VMAT radiotherapy treatments. More efficient methods for pre-treatment PSQA, like EPID based measurements, can balance optimal quality assurance on patient plans and time sparing. However, these methods are discouraged by the AAPM TG 218 for VMAT plans because “using the EPID to obtain an integrated image for VMAT is considered PC” (Perpendicular Composite). As recently reported by the AAPM TG 307 few studies compare traditional methods of pre-treatment PSQA (i.e., based on ionization chambers or diodes arrays) with EPID measurements, and, to the best of our knowledge, none of them reports results on the SunNuclear SunCheck Patient software. This study aims then to compare PSQA obtained with this system against a well-established TC (True Composite) method for pre-treatment QA such as the SunNuclear ArcCheck diodes array to investigate the possibility of replacing traditional pre-treatment PSQA methods with EPID measurements. Thirty VMAT plans were repeatedly measured, on a Varian TrueBeam v2.7 linac, with ArcCheck in a composite way and with EPID per field, registering an integrated EPID image of each arc. All VMAT plans were characterized by two or three arcs. The linac output was measured before each measurement session, being within ±0.5% the reference value. Pre-treatment EPID images, acquired without couch and/or phantoms, were converted into planar dose in a water slab at the EPID level by the PerFRACTION module of the SunCheck Patient software as Fraction 0 and were successively compared, through gamma-analysis, with calculated dose maps obtained by the embedded SunNuclear DoseCheck algorithm. ArcCheck measurements were performed in absolute dose to water by previous calibration of the instrument and were compared with the TPS calculations (Varian Acuros XB algorithm, reported in dose-to-water). Gamma Passing Rates (GPR) for both the comparisons in absolute doses were registered with different dose-DTA criteria, namely, 3%2mm, 3%1mm, 2%2mm, 2%1mm, 1%2mm, 1%1mm, all global and with threshold at 10%. For each approach, GPR distributions were analyzed and the main statistic descriptors (i.e., median, inter-quartile range, maximum and minimum) were computed alongside with the correlation between each GPR distribution obtained Material/Methods: