title: Reproducibility of MRI-determined proton density fat fraction across two different MR scanner platforms.
abstract: OBJECTIVE
  To evaluate magnetic resonance imaging (MRI)-determined proton density fat fraction (PDFF) reproducibility across two MR scanner platforms and, using MR spectroscopy (MRS)-determined PDFF as reference standard, to confirm MRI-determined PDFF estimation accuracy.
  
  
  METHODS
  This prospective, cross-sectional, crossover, observational pilot study was approved by an Institutional Review Board. Twenty-one subjects gave written informed consent and underwent liver MRI and MRS at both 1.5T (Siemens Symphony scanner) and 3T (GE Signa Excite HD scanner). MRI-determined PDFF was estimated using an axial 2D spoiled gradient-recalled echo sequence with low flip-angle to minimize T1 bias and six echo-times to permit correction of T2* and fat-water signal interference effects. MRS-determined PDFF was estimated using a stimulated-echo acquisition mode sequence with long repetition time to minimize T1 bias and five echo times to permit T2 correction. Interscanner reproducibility of MRI determined PDFF was assessed by correlation analysis; accuracy was assessed separately at each field strength by linear regression analysis using MRS-determined PDFF as reference standard.
  
  
  RESULTS
  1.5T and 3T MRI-determined PDFF estimates were highly correlated (r = 0.992). MRI-determined PDFF estimates were accurate at both 1.5T (regression slope/intercept = 0.958/-0.48) and 3T (slope/intercept = 1.020/0.925) against the MRS-determined PDFF reference.
  
  
  CONCLUSIONS
  MRI-determined PDFF estimation is reproducible and, using MRS-determined PDFF as reference standard, accurate across two MR scanner platforms at 1.5T and 3T.
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego Medical Center, University of California at San Diego, MR3T Laboratory, San Diego, California 92103-8226, USA.
authors.forename: Geraldine H
authors.initials: GH
authors.lastname: Kang
authors.forename: Irene
authors.initials: I
authors.lastname: Cruite
authors.forename: Masoud
authors.initials: M
authors.lastname: Shiehmorteza
authors.forename: Tanya
authors.initials: T
authors.lastname: Wolfson
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Gamst
authors.forename: Gavin
authors.initials: G
authors.lastname: Hamilton
authors.forename: Mark
authors.initials: M
authors.lastname: Bydder
authors.forename: Michael S
authors.initials: MS
authors.lastname: Middleton
authors.forename: Claude B
authors.initials: CB
authors.lastname: Sirlin
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D002648:Child; D002908:Chronic Disease; D018592:Cross-Over Studies; D003430:Cross-Sectional Studies; D005234:Fatty Liver / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease; D010865:Pilot Projects; D011446:Prospective Studies; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D055815:Young Adult