ESTRO 2024 - Abstract Book

S3244

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

with the two different detectors. For the EPID measurements the per plan GPR (i.e., the average of GPR values obtained for each plan arc) was considered. Action limits, as suggested by the AAPM TG 218, have been also calculated for each considered dose-DTA criterium.

Results:

Descriptive statistics (i.e., median, inter-quartile range, maximum and minimum) of the recorded GPRs is reported in Table with the action limits calculated as suggested by the AAPM TG 218. For EPID measurements the average of GPR values obtained for each plan arc have been reported. These data show a general overlap between all the reported GPR distributions, then no further statistical analyses have been performed to find differences between groups. Pearson correlation coefficients calculated from each combination of GPR distributions with ArcCheck and EPID, range form -0,23 to 0,83 corresponding respectively to the relationship between 1%1mm criterium for ArcCheck and 1%2mm criterium for PerFraction-Fraction0 and between 3%2mm criterium for ArcCheck and 3%1mm criterium for PerFraction-Fraction0. This maximal correlation suggests using for EPID measurements the 3%1mm criterium as a twin of the AAPM TG 218 universal criterium for TC pre-treatment PSQA, i.e., 3%2mm.

Conclusion:

Our comparison between the EPID pre-treatment PSQA system SunCheck PerFRACTION and ArcCheck, on a sample of thirty VMAT plans, shows no significant differences in GPRs distributions for different dose-DTA criteria, suggesting the possibility of using this EPID pre-treatment dosimetry system, less time consuming, as substitute of a traditional TC pre-treatment PSQA method like ArcCheck, provided that proper dose-DTA criteria and action limits are chosen. Further data obtained also in a multicentric contest will be certainly needed to corroborate these statements.

Keywords: PerFRACTION, ArcCheck, PSQA.