The effects of concomitant gradients on chemical shift encoded MRI
Timothy J Colgan1,2, Diego Hernando1,2, Samir D Sharma1
1Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
Purpose:
The purpose of this work was to characterize the effects of concomitant gradients (CGs) on chemical shift encoded (CSE)-based estimation of B0 field map, proton density fat fraction (PDFF), and R2*.
Theory:
A theoretical framework was used to determine the effects of CG-induced phase errors on CSE-MRI data.
Methods:
Simulations, 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.
Results:
Phase errors attributed to CGs introduce errors in the estimation of B0 field map, PDFF, and R2*. Phantom and in vivo experiments demonstrated that CGs can introduce estimation errors greater than 30 Hz in the B0 field map, 10% in PDFF, and 16 s-1 in R2*, 16 cm off isocenter. However, CG phase correction before parameter estimation was able to reduce estimation errors to less than 10 Hz in the B0 field map, 1% in PDFF, and 2 s-1 in R2*.
Conclusion:
CG effects can impact CSE-MRI, leading to inaccurate estimation of B0 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. © 2016 International Society for Magnetic Resonance in Medicine.
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