title: Reproducibility of hepatic fat fraction measurement by magnetic resonance imaging.
abstract: OBJECTIVE
  To evaluate the reproducibility of magnetic resonance imaging (MRI)-determined hepatic fat fraction (%) across imaging sites with different magnet types and field strength. Reproducibility among MRI platforms is unclear, even though evaluating hepatic fat fractions (FFs) using MRI-based methods is accurate against MR spectroscopy.
  
  
  METHODS
  Overweight subjects were recruited to undergo eight MRI examinations at five imaging centers with a range of magnet manufacturers and field strengths (1.5 and 3 T). FFs were estimated in liver and in fat-emulsion phantoms using three methods: 1) dual-echo images without correction (nominally out-of-phase [OP] and in-phase [IP]); 2) dual-dual-echo images (two sequences) with T2* correction (nominally OP/IP and IP/IP); and 3) six-echo images with spectral model and T2* correction, at sequential alternating OP and IP echo times (Methods 1, 2, and 3, respectively).
  
  
  RESULTS
  Ten subjects were recruited. For Methods 1, 2, and 3, respectively, hepatic FF ranged from -2.5 to 27.0, 1.9 to 29.6, and 1.3 to 34.4%. Intraclass correlation coefficients were 0.85, 0.89, and 0.91 for each method, and within-subject coefficients of variation were 18.5, 9.9, and 10.3%, respectively. Mean phantom FFs derived by Methods 2 and 3 were comparable to the known FF for each phantom. Method 1 underestimated phantom FF.
  
  
  CONCLUSIONS
  Methods 2 and 3 accurately assess FF. Strong reproducibility across magnet type and strength render them suitable for use in multicenter trials and longitudinal assessments.
authors.affiliation: Radiology, University of California/San Diego, San Diego, California, USA.
authors.forename: Arian
authors.initials: A
authors.lastname: Mashhood
authors.forename: Radha
authors.initials: R
authors.lastname: Railkar
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yokoo
authors.forename: Yakir
authors.initials: Y
authors.lastname: Levin
authors.forename: Lisa
authors.initials: L
authors.lastname: Clark
authors.forename: Sabrina
authors.initials: S
authors.lastname: Fox-Bosetti
authors.forename: Michael S
authors.initials: MS
authors.lastname: Middleton
authors.forename: Jonathan
authors.initials: J
authors.lastname: Riek
authors.forename: Eunkyung
authors.initials: E
authors.lastname: Kauh
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Dardzinski
authors.forename: Donald
authors.initials: D
authors.lastname: Williams
authors.forename: Claude
authors.initials: C
authors.lastname: Sirlin
authors.forename: Norah J
authors.initials: NJ
authors.lastname: Shire
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D050154:Adiposity; D005234:Fatty Liver / Q000150:complications / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease; D009765:Obesity / Q000150:complications / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States