Factors influencing daily quality assurance measurements of magnetic resonance imaging scanners

Magnetic resonance imaging is commonly used in hospitals and clinics to aid medical diagnoses. Scanner performance should be assessed regularly, including daily, weekly, and yearly evaluations to ensure high-quality and artifact-free images. Of these assessments, the daily quality assurance monitors the image quality of the scanner using a manufacturer-provided protocol. In this study, we sought to determine the factors that introduced variability in daily quality assurance data. A phantom was scanned using a head coil in two schemes: with varied phantom placement daily, and with a single phantom placement, and evaluated over approximately 1 month. Minor placement and localization changes accounted for approximately 50% of the variability in the signal-to-noise ratios observed in these measures, driven by changes in the measured signal, while the noise remained constant. The changes in the signal-to-noise ratios were small over the 2-month study period.