Are Acceptance Tests Still Necessary for Quality Control Equipment That Is Already Widely Implemented In Other Hospitals?
Abstract
Purpose
To share our experience with the acceptance testing of nine myQA Daily devices (IBA) and to evaluate the relevance of these tests despite the system being widely used clinically in other hospitals.
Methods
Following installation of nine myQA Daily devices (IBA), acceptance tests were performed to assess reproducibility, field size accuracy, linearity with monitor units and dose rate, symmetry and flatness. Reproducibility was evaluated using ten irradiations of a 100 MU, 20 × 20 cm² field. Field size measurements were compared with EPID analysis. Linearity was assessed against a PTW 30013 Farmer ionization chamber over a range of 2–1000 MU and 400–1000 MU/min. Symmetry and flatness measurements were compared with an IC Profiler (Sun Nuclear Corporation) following controlled modifications of the accelerator magnet current.
Results
Reproducibility was excellent, with a maximum standard deviation of 0.1%. The myQA Daily slightly overestimated field size compared with the EPID, with a mean difference of 2.5 mm. Linearity with monitor units agreed within 0.5% above 10 MU but deviated by up to 4% below this threshold. The linearity with dose rate varies in comparison with the ionisation chamber about 0.6% for the highest dose rate. For symmetry in comparison with IC Profiler, we found out a region of symmetry values where myQA Daily was not able to detect the symmetry change. This limitation was due to the symmetry equation implemented in the device software. The flatness agreed within 0.5% with the IC Profiler.
Conclusion
Acceptance testing identified a software-related symmetry calculation issue that was subsequently corrected. These results highlight the importance of acceptance testing, even for quality assurance devices already in widespread clinical use.