title: Quantification of hepatic steatosis with MRI: the effects of accurate fat spectral modeling.
abstract: OBJECTIVE
  To develop a chemical-shift-based imaging method for fat quantification that accounts for the complex spectrum of fat, and to compare this method with MR spectroscopy (MRS). Quantitative noninvasive biomarkers of hepatic steatosis are urgently needed for the diagnosis and management of nonalcoholic fatty liver disease (NAFLD).
  
  
  METHODS
  Hepatic steatosis was measured with "fat-fraction" images in 31 patients using a multiecho chemical-shift-based water-fat separation method at 1.5T. Fat-fraction images were reconstructed using a conventional signal model that considers fat as a single peak at -210 Hz relative to water ("single peak" reconstruction). Fat-fraction images were also reconstructed from the same source images using two methods that account for the complex spectrum of fat; precalibrated and self-calibrated "multipeak" reconstruction. Single-voxel MRS that was coregistered with imaging was performed for comparison.
  
  
  RESULTS
  Imaging and MRS demonstrated excellent correlation with single peak reconstruction (r(2) = 0.91), precalibrated multipeak reconstruction (r(2) = 0.94), and self-calibrated multipeak reconstruction (r(2) = 0.91). However, precalibrated multipeak reconstruction demonstrated the best agreement with MRS, with a slope statistically equivalent to 1 (0.96 +/- 0.04; P = 0.4), compared to self-calibrated multipeak reconstruction (0.83 +/- 0.05, P = 0.001) and single-peak reconstruction (0.67 +/- 0.04, P < 0.001).
  
  
  CONCLUSIONS
  Accurate spectral modeling is necessary for accurate quantification of hepatic steatosis with MRI.
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA. sreeder@wisc.edu
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
authors.forename: Philip M
authors.initials: PM
authors.lastname: Robson
authors.forename: Huanzhou
authors.initials: H
authors.lastname: Yu
authors.forename: Ann
authors.initials: A
authors.lastname: Shimakawa
authors.forename: Catherine D G
authors.initials: CD
authors.lastname: Hines
authors.forename: Charles A
authors.initials: CA
authors.lastname: McKenzie
authors.forename: Jean H
authors.initials: JH
authors.lastname: Brittain
mesh_terms: D000328:Adult; D000368:Aged; D005234:Fatty Liver / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies