Assessing effects of scanner upgrades for clinical studies.

Background Scanner upgrades due to software and hardware changes are an inevitable part of MR research and, without quality assurance protocols, can jeopardize studies. Purpose To evaluate changes in T-1 relaxation time by inversion recovery (IR) and variable flip angle (VFA) measurements on a 3T system that underwent an "everything but the magnet" upgrade. Study Type Longitudinal. Phantom An International Society of Magnetic Resonance in Medicine / National Institute of Standards and Technology (ISMRM/NIST) system phantom with repeated measurements across multiple (n = 3) days. Field Strength/Sequence T-1 IR, VFA at 3T. Assessment The T-1 measurements by IR and VFA were compared with the nuclear magnetic resonance (NMR) measurements, which constitute the known values for the ISMRM/NIST system phantom, to determine the measurement error. Statistical Tests Descriptive. Results The T-1 VFA measurement errors were distributed around zero (-15% to +10%) on the original system and then the errors were distributed entirely above zero post-upgrade (+5% to 30%). The T-1 IR results had a dramatic increase in error distribution (+/- 5% original, +/- 20% post-upgrade) prior to the identification of signal saturation as an issue. Once the signal saturation was accounted for, the T-1 IR errors decreased to +/- 10% post-upgrade. Data Conclusion The T-1 VFA measurement differences between the original and post-upgrade systems can be entirely attributed to contributions from B-1. The T-1 IR measurements demonstrate the need for quantitative quality assurance (QA) processes. The site under study passed the QA protocols in place, which did not identify the increased T-1 error, nor the signal saturation issue. To improve on this study, we would make systematic, quantitative measurements at intervals less than a year and following any hardware or software upgrade. Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2019;50:1948-1954.