title: Hepatic fat quantification: a prospective comparison of magnetic resonance spectroscopy and analysis methods for chemical-shift gradient echo magnetic resonance imaging with histologic assessment as the reference standard.
abstract: OBJECTIVE
  The aims of this study were to assess the confounding effects of hepatic iron deposition, inflammation, and fibrosis on hepatic steatosis (HS) evaluation by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) and to assess the accuracies of MRI and MRS for HS evaluation, using histology as the reference standard.
  
  
  METHODS
  In this institutional review board-approved prospective study, 56 patients gave informed consents and underwent chemical-shift MRI and MRS of the liver on a 1.5-T magnetic resonance scanner. To estimate MRI fat fraction (FF), 4 analysis methods were used (dual-echo, triple-echo, multiecho, and multi-interference), and MRS FF was calculated with T2 correction. Degrees of HS, iron deposition, inflammation, and fibrosis were analyzed in liver resection (n = 37) and biopsy (n = 19) specimens. The confounding effects of histology on fat quantification were assessed by multiple linear regression analysis. Using the histologic degree of HS as the reference standard, the accuracies of each method in estimating HS and diagnosing an HS of 5% or greater were determined by linear regression and receiver operating characteristic analyses.
  
  
  RESULTS
  Iron deposition significantly confounded estimations of FF by the dual-echo (P < 0.001) and triple-echo (P = 0.033) methods, whereas no histologic feature confounded the multiecho and multi-interference methods or MRS. The MRS (r = 0.95) showed the strongest correlation with histologic degree of HS, followed by the multiecho (r = 0.92), multi-interference (r = 0.91), triple-echo (r = 0.90), and dual-echo (r = 0.85) methods. For diagnosing HS, the areas under the curve tended to be higher for MRS (0.96) and the multiecho (0.95), multi-interference (0.95), and triple-echo (0.95) methods than for the dual-echo method (0.88) (P ≥ 0.13).
  
  
  CONCLUSIONS
  The multiecho and multi-interference MRI methods and MRS can accurately quantify hepatic fat, with coexisting histologic abnormalities having no confounding effects.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
authors.forename: Bo-Kyeong
authors.initials: BK
authors.lastname: Kang
authors.forename: Eun Sil
authors.initials: ES
authors.lastname: Yu
authors.forename: Seung Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Youngjoo
authors.initials: Y
authors.lastname: Lee
authors.forename: Namkug
authors.initials: N
authors.lastname: Kim
authors.forename: Claude B
authors.initials: CB
authors.lastname: Sirlin
authors.forename: Eun Yoon
authors.initials: EY
authors.lastname: Cho
authors.forename: Suk Keu
authors.initials: SK
authors.lastname: Yeom
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Byun
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Moon-Gyu
authors.initials: MG
authors.lastname: Lee
mesh_terms: D000273:Adipose Tissue; D050154:Adiposity; D000328:Adult; D000368:Aged; D017352:Echo-Planar Imaging / Q000379:methods* / Q000592:standards; D005234:Fatty Liver / Q000175:diagnosis* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007501:Iron / Q000032:analysis*; D008099:Liver; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D056910:Republic of Korea
chemical_list: D007501:Iron