Bland and Altman analysis: Machine performance check output

Abstract

Background: The aim of this study was to evaluate the variation in the daily output of a linac Varian Edge TrueBeam over a month, using a Daily QA3 (QA3) and machine performance check (MPC), after Task Group 51protocol and baseline data had been established. Methods and Materials: The daily output data were collected for all photons (6, 10 MV, and 6, 10 FFF) and electrons (6, 9, 12, and 15 MeV) energies. A Bland-Altman-Plot and intraclass correlation coefficients were used to assess agreement and reliability. Results: MPC data showed small random deviations of ≤ 2% and agreed with the QA3 measurements. The maximum mean absolute difference between the QA3 and MPC data was observed with 6 MeV (0.5633), with limits of agreement of (−0.5392–1.6658). Conclusion: These results suggest that MPC data closely track QA3 data and that the two forms are interchangeable