title: The effects of concomitant gradients on chemical shift encoded MRI.
abstract: The purpose of this work was to characterize the effects of concomitant gradients (CGs) on chemical shift encoded (CSE)-based estimation of B0field map, proton density fat fraction (PDFF), and R2*.
  
  
  
  A theoretical framework was used to determine the effects of CG-induced phase errors on CSE-MRI data.
  
  
  
  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.
  
  
  
  Phase errors attributed to CGs introduce errors in the estimation of B0field map, PDFF, and R2*. Phantom and in vivo experiments demonstrated that CGs can introduce estimation errors greater than 30 Hz in the B0field map, 10% in PDFF, and 16 s-1in 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 B0field map, 1% in PDFF, and 2 s-1in R2*.
  
  
  
  CG effects can impact CSE-MRI, leading to inaccurate estimation of B0field 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.
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Colgan
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Hernando
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Samir D
authors.initials: SD
authors.lastname: Sharma
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.|Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA.|Department of Medicine, University of Wisconsin, Madison, Wisconsin, USA.|Department of Emergency Medicine, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007866:Leg / Q000000981:diagnostic imaging; D008099:Liver / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging
keywords: 
  R2* estimation; B0 field map estimation; PDFF; chemical shift encoded MRI; concomitant gradients; iron quantification