Six-year data from three magnetic resonance-guided radiotherapy systems demonstrate long-term stability of linear accelerator quality assurance.

Abstract

Background and purposeMagnetic resonance-guided radiotherapy systems require comprehensive quality assurance (QA) programs to ensure safe and precise treatment delivery. This study evaluates the long-term behavior and variability of linac-related QA results across three clinically operated 1.5 T MRI-linacs at a single institution and assesses compliance with tolerance limits.Materials and methodsQA data acquired over a six-year period from three clinically operated 1.5 T MRI-linacs were retrospectively analyzed. A range of linac-related dosimetric and mechanical QA tests was included. Performance envelopes (mean ± 2 SD) were constructed to characterize variability relative to tolerance limits.ResultsFor 11 of 13 QA tests, performance envelopes for the associated metrics remained within the applied tolerance limits. For the two remaining tests, envelopes slightly extended beyond these limits. These deviations were not considered clinically relevant, and their underlying causes were understood. No progressive trends of clinical relevance were observed in the linac-specific time series.ConclusionsStability of linac-related QA results was demonstrated over six years across three MRI-linacs, supporting reconsideration of the QA program.