ESTRO 2025 - Abstract Book

S3642

Physics - Quality assurance and auditing

ESTRO 2025

Material/Methods: Twenty high-complexity SABR treatment plans, created using Raystation (V10B, Raysearch, Sweden) treatment planning system (TPS), were analysed. Plans were recalculated on both Compass and myQA iON, and the doses were compared to TPS dose using gamma analysis with 2%/2mm and 3%3mm gamma criteria. Dose metrics including gamma pass rate and PTV dose differences were assessed. For the measurement systems, MatrixX and SRS detector dose distributions were compared to TPS using gamma analysis (2%/2mm, 3%/3mm). Statistical differences between systems were evaluated using paired t-tests. The correlation between plan complexity indices and PSQA results was analysed using Spearman’s correlation. Lastly, MLC errors were introduced to one plan using a python script. Original and erroneous plans were delivered to the measurement devices to assess their ability to detect these errors. Results: Analysis of the independent dose calculation systems revealed a statistically significant difference in average PTV dose differences between Compass and myQAion (t=-9.72, two-sided p<0.001, 95% CI -4.51, -2.91). No significant differences were found in gamma pass rates for either calculation or measurement systems.

Correlation analysis identified a strong, statistically significant relationship between the MatrixX measurement results and the field irregularity (FI) complexity index (r=-0.800, p<0.001) while a moderate weakly significant correlation was observed between the FI and the SRS detector results (r=-0.416, p=0.068). Both detectors were able to detect 1 mm MLC offset errors when applying a 1%/1 mm gamma criterion.