title: Accuracy of multiecho magnitude-based MRI (M-MRI) for estimation of hepatic proton density fat fraction (PDFF) in children.
abstract: OBJECTIVE
  To assess accuracy of magnitude-based magnetic resonance imaging (M-MRI) in children to estimate hepatic proton density fat fraction (PDFF) using two to six echoes, with magnetic resonance spectroscopy (MRS) -measured PDFF as a reference standard.
  
  
  METHODS
  This was an IRB-approved, HIPAA-compliant, single-center, cross-sectional, retrospective analysis of data collected prospectively between 2008 and 2013 in children with known or suspected nonalcoholic fatty liver disease (NAFLD). Two hundred eighty-six children (8-20 [mean 14.2 ± 2.5] years; 182 boys) underwent same-day MRS and M-MRI. Unenhanced two-dimensional axial spoiled gradient-recalled-echo images at six echo times were obtained at 3T after a single low-flip-angle (10°) excitation with ≥ 120-ms recovery time. Hepatic PDFF was estimated using the first two, three, four, five, and all six echoes. For each number of echoes, accuracy of M-MRI to estimate PDFF was assessed by linear regression with MRS-PDFF as reference standard. Accuracy metrics were regression intercept, slope, average bias, and R(2) .
  
  
  RESULTS
  MRS-PDFF ranged from 0.2-40.4% (mean 13.1 ± 9.8%). Using three to six echoes, regression intercept, slope, and average bias were 0.46-0.96%, 0.99-1.01, and 0.57-0.89%, respectively. Using two echoes, these values were 2.98%, 0.97, and 2.72%, respectively. R(2) ranged 0.98-0.99 for all methods.
  
  
  CONCLUSIONS
  Using three to six echoes, M-MRI has high accuracy for hepatic PDFF estimation in children.
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Zand
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Amol
authors.initials: A
authors.lastname: Shah
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Elhamy
authors.initials: E
authors.lastname: Heba
authors.affiliation: Computational and Applied Statistics Laboratory, Division of Biostatistics and Informatics, University of California, San Diego, California, USA.
authors.forename: Tanya
authors.initials: T
authors.lastname: Wolfson
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Gavin
authors.initials: G
authors.lastname: Hamilton
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Lam
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Chen
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Hooker
authors.affiliation: Computational and Applied Statistics Laboratory, Division of Biostatistics and Informatics, University of California, San Diego, California, USA.
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Gamst
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Middleton
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.|Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of California, San Diego, California, USA.|Department of Gastroenterology, Rady Children's Hospital, San Diego, California, USA.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Schwimmer
authors.affiliation: Liver Imaging Group, Department of Radiology, University of California, San Diego, California, USA.
authors.forename: Claude B
authors.initials: CB
authors.lastname: Sirlin
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003430:Cross-Sectional Studies; D005234:Fatty Liver / Q000473:pathology*; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011522:Protons; D015203:Reproducibility of Results; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D011522:Protons
keywords: MRI; MRS; NAFLD; PDFF; liver steatosis; proton density fat fraction
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