Table 3.

Test frequencies and intervention thresholds for regular quality assurance

Parameter	Minimum requirement	Additional recommendation	Optional
End-to-end test including MRI simulation	Yearly, after commissioning and after changes to the SRT treatment planning chain in accordance with DIN 6864‑1	–	–
Residual gradient non-linearity-related distortions after vendor 3D correction	Characterize using phantom measurements at the time of commissioning, after scanner upgrades, repairs or maintenance, and at least in yearly intervals. Maximum amount of distortion obtained via phantom measurements for the field-of-view of a typical head MRI scan (sphere of 25 cm diameter) must not exceed 1 mm	In addition to minimum requirements: Characterization of residual gradient non-linearity related distortions in at least monthly intervals using phantom measurements	In addition to additional recommendations: Correction of residual distortions ≤ 1 mm based on phantom measurements
Main magnetic field (B0) homogeneity	Characterize after installation (baseline), after scanner upgrades, repairs or maintenance, and at least in yearly intervals, as detailed in sources such as [32] and [33]. If necessary, arrange for repairs to maintain field homogeneity and ensure necessary geometric accuracy	–	In addition to minimum requirements: Individually characterize main magnetic field inhomogeneities from system imperfections and susceptibility-related inhomogeneities for patients undergoing MRI simulation by using B0 mapping. Perform individual corrections based on individual B0 mapping or reverse gradient methods
Screening for metallic objects	Daily check the scanner bore for small metallic objects; Check gradient echo-based localizer images for metal artifacts in every patient	–	–
Registration algorithm	Registration error within ≤ 1 mm for registration of phantoms at commissioning	–	–
Image quality for flexible coil systems	–	–	Monthly