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Sensitivity and concordance study of an open source EPID‐based linear accelerator test suite

L. Critchfield, C. Knill, E. Durussel, J. Mikell, Michael P. Barnes, M. Pillainayagam, W. Donahue, S. Lim et al.

Journal of Applied Clinical Medical Physics, 2026

Abstract

Abstract Background Electronic portal imaging devices (EPIDs) enhance linear accelerator (linac) quality assurance (QA) efficiency but are not universally used beyond patient‐specific IMRT QA. A multi‐institutional Consortium seeks to standardize linac QA utilizing an EPID‐based test suite. Purpose This study evaluates the sensitivity of a test suite to intentional linac and plan errors and the concordance with linac fluctuations over time. Methods Baseline and error‐introduced tests were performed on a Varian TrueBeam and Clinac. Evaluated parameters included enhanced dynamic wedge factors (EDW) (6MV), central axis dose (6MV, 6MV FFF, 16MV), focal spot alignment and beam symmetry (6MV, 16MV), dose rate‐gantry speed and multi‐leaf collimator (MLC) leaf speed (6MV). Errors included varying EDW angles (10°–60°), output changes, beam steering for focal spot and symmetry inaccuracies, and meterset adjustments of control points for dose rate‐gantry speed and MLC leaf speed tests. Measurements were performed with an EPID, analyzed via test suite software, and compared to an ion chamber (IC) or array. Concordance analysis was performed on a single linac over 5 months to assess the test suite's ability to quantify deviations during routine operations. Measurement reproducibility was assessed. Results Results were reported as differences between EPID and an IC or array. For each EDW, wedge factor differences were 0.99), though EPID measurements underestimated changes in symmetry…

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