title: Improving chemical shift encoded water-fat separation using object-based information of the magnetic field inhomogeneity.
abstract: OBJECTIVE
  The purpose of this work was to improve the robustness of existing chemical shift encoded water-fat separation methods by incorporating object-based information of the B0 field inhomogeneity.
  
  
  BACKGROUND
  The primary challenge in water-fat separation is the estimation of phase shifts that arise from B0 field inhomogeneity, which is composed of the background field and susceptibility-induced field. The susceptibility-induced field can be estimated if the susceptibility distribution is known or can be approximated. In this work, the susceptibility distribution is approximated from the source images using the known susceptibility values of water, fat, and air. The field estimate is then demodulated from the source images before water-fat separation.
  
  
  METHODS
  Chemical shift encoded source images were acquired in anatomical regions that are prone to water-fat swaps. The images were processed using algorithms from the ISMRM Fat-Water Toolbox, with and without the object-based field map information. The estimates were compared to examine the benefit of using the object-based field map information.
  
  
  RESULTS
  Multiple cases are shown in which water-fat swaps were avoided by using the object-based information of the B0 field map.
  
  
  CONCLUSIONS
  Object-based information of the B0 field may improve the robustness of existing chemical shift encoded water-fat separation methods.
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Samir D
authors.initials: SD
authors.lastname: Sharma
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Artz
authors.forename: Diego
authors.initials: D
authors.lastname: Hernando
authors.forename: Debra E
authors.initials: DE
authors.lastname: Horng
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology*; D000465:Algorithms; D000842:Ankle / Q000033:anatomy & histology*; D001834:Body Water / Q000166:cytology*; D001917:Brachial Plexus / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010363:Pattern Recognition, Automated / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: B0 field estimation; Dixon imaging; chemical shift encoded water-fat separation; magnetic resonance imaging; susceptibility; water-fat imaging