The effects of concomitant gradients on chemical shift encoded MRI

PurposeThe purpose of this work was to characterize the effects of concomitant gradients (CGs) on chemical shift encoded (CSE)-based estimation of B-0 field map, proton density fat fraction (PDFF), and R2*. TheoryA theoretical framework was used to determine the effects of CG-induced phase errors on CSE-MRI data. MethodsSimulations, phantom experiments, and in vivo experiments were conducted at 3 Tesla to assess the effects of CGs on quantitative CSE-MRI techniques. Correction of phase errors attributable to CGs was also investigated to determine whether these effects could be removed. ResultsPhase errors attributed to CGs introduce errors in the estimation of B-0 field map, PDFF, and R-2*. Phantom and in vivo experiments demonstrated that CGs can introduce estimation errors greater than 30Hz in the B-0 field map, 10% in PDFF, and 16 s(-1) in R-2*, 16cm off isocenter. However, CG phase correction before parameter estimation was able to reduce estimation errors to less than 10Hz in the B-0 field map, 1% in PDFF, and 2 s(-1) in R-2*. ConclusionCG effects can impact CSE-MRI, leading to inaccurate estimation of B-0 field map, PDFF, and R2*. However, correction for phase errors caused by CGs improve the accuracy of quantitative parameters estimated from CSE-MRI acquisitions. Magn Reson Med 78:730-738, 2017. (c) 2016 International Society for Magnetic Resonance in Medicine