title: Quantification of liver fat in the presence of iron overload.
abstract: To evaluate the accuracy of R2* models (1/T2* = R2*) for chemical shift-encoded magnetic resonance imaging (CSE-MRI)-based proton density fat-fraction (PDFF) quantification in patients with fatty liver and iron overload, using MR spectroscopy (MRS) as the reference standard.
  
  
  
  Two Monte Carlo simulations were implemented to compare the root-mean-squared-error (RMSE) performance of single-R2* and dual-R2* correction in a theoretical liver environment with high iron. Fatty liver was defined as hepatic PDFF >5.6% based on MRS; only subjects with fatty liver were considered for analyses involving fat. From a group of 40 patients with known/suspected iron overload, nine patients were identified at 1.5T, and 13 at 3.0T with fatty liver. MRS linewidth measurements were used to estimate R2* values for water and fat peaks. PDFF was measured from CSE-MRI data using single-R2* and dual-R2* correction with magnitude and complex fitting.
  
  
  
  Spectroscopy-based R2* analysis demonstrated that the R2* of water and fat remain close in value, both increasing as iron overload increases: linear regression between R2*Wand R2*Fresulted in slope = 0.95 [0.79-1.12] (95% limits of agreement) at 1.5T and slope = 0.76 [0.49-1.03] at 3.0T. MRI-PDFF using dual-R2* correction had severe artifacts. MRI-PDFF using single-R2* correction had good agreement with MRS-PDFF: Bland-Altman analysis resulted in -0.7% (bias) ± 2.9% (95% limits of agreement) for magnitude-fit and -1.3% ± 4.3% for complex-fit at 1.5T, and -1.5% ± 8.4% for magnitude-fit and -2.2% ± 9.6% for complex-fit at 3.0T.
  
  
  
  Single-R2* modeling enables accurate PDFF quantification, even in patients with iron overload.
  
  
  
  1 J. Magn. Reson. Imaging 2017;45:428-439.
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.|Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Debra E
authors.identifier: 0000-0001-7146-0838
authors.initials: DE
authors.lastname: Horng
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Hernando
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.|Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, USA.|Department of Medicine, University of Wisconsin, Madison, Wisconsin, USA.|Department of Emergency Medicine, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000473:pathology; D050154:Adiposity; D000328:Adult; D002648:Child; D005234:Fatty Liver / Q000000981:diagnostic imaging* / Q000209:etiology / Q000473:pathology; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019190:Iron Overload / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: chemical shift-encoded magnetic resonance imaging; iron overload; liver fat