A National Survey of Factors Influencing Psqa Measurement Frequency for VMAT and SBRT In Canada
Abstract
Purpose
To characterize patient‑specific quality assurance (PSQA) measurement frequency patterns across Canadian radiotherapy centers and to identify factors associated with reduced PSQA measurement frequency for routine VMAT and SBRT deliveries. The survey scope was limited to these two modalities.
Methods
A national survey was distributed in 2024 to all Canadian radiotherapy centers to document PSQA practices, available verification tools, and the rationales guiding local decision‑making. Respondents indicated whether their PSQA measurement frequency for VMAT and/or SBRT had been reduced relative to their historical baseline and, if so, provided justification. Centers also reported the verification tools they used, enabling analysis of associations between tool selection, center characteristics, and practice patterns.
Results
Fifty‑three percent of centers (n = 24) reported reducing PSQA measurement frequency for VMAT and/or SBRT, while forty‑seven percent (n = 21) continued measuring all patient plans. Among centers that reduced frequency, the most common justification was having accumulated sufficient measurements without failures (79 percent). Additional reasons included data‑driven approaches (38 percent), plan‑metric‑based methods (29 percent), and risk analysis (13 percent). No center cited published guidelines. Centers using delivery‑log‑based verification showed the highest rates of reduced frequency, consistent with substituting routine measurements with log analysis within a hybrid PSQA workflow. In contrast, most centers relying primarily on EPID dosimetry did not reduce frequency, likely due to its lower resource burden. Larger centers were more likely to report reductions, suggesting confidence derived from accumulated experience and available resources.
Conclusion
This survey highlights clear national trends in how Canadian centers are adapting PSQA measurement frequency based on internal data, verification tools, and operational experience. While practices remain heterogeneous, the findings provide a contemporary snapshot that may support future efforts toward consistency and the development of guidance aligned with diverse clinical environments.