title: Quantification of liver fat with respiratory-gated quantitative chemical shift encoded MRI.
abstract: OBJECTIVE
  To evaluate free-breathing chemical shift-encoded (CSE) magnetic resonance imaging (MRI) for quantification of hepatic proton density fat-fraction (PDFF). A secondary purpose was to evaluate hepatic R2* values measured using free-breathing quantitative CSE-MRI.
  
  
  METHODS
  Fifty patients (mean age, 56 years) were prospectively recruited and underwent the following four acquisitions to measure PDFF and R2*; 1) conventional breath-hold CSE-MRI (BH-CSE); 2) respiratory-gated CSE-MRI using respiratory bellows (BL-CSE); 3) respiratory-gated CSE-MRI using navigator echoes (NV-CSE); and 4) single voxel MR spectroscopy (MRS) as the reference standard for PDFF. Image quality was evaluated by two radiologists. MRI-PDFF measured from the three CSE-MRI methods were compared with MRS-PDFF using linear regression. The PDFF and R2* values were compared using two one-sided t-test to evaluate statistical equivalence.
  
  
  RESULTS
  There was no significant difference in the image quality scores among the three CSE-MRI methods for either PDFF (P = 1.000) or R2* maps (P = 0.359-1.000). Correlation coefficients (95% confidence interval [CI]) for the PDFF comparisons were 0.98 (0.96-0.99) for BH-, 0.99 (0.97-0.99) for BL-, and 0.99 (0.98-0.99) for NV-CSE. The statistical equivalence test revealed that the mean difference in PDFF and R2* between any two of the three CSE-MRI methods was less than ±1 percentage point (pp) and ±5 s(-1) , respectively (P < 0.046).
  
  
  CONCLUSIONS
  Respiratory-gated CSE-MRI with respiratory bellows or navigator echo are feasible methods to quantify liver PDFF and R2* and are as valid as the standard breath-hold technique.
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Radiology, University of Yamanashi, Yamanashi, Japan.
authors.forename: Utaroh
authors.initials: U
authors.lastname: Motosugi
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Hernando
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Radiology, University Hospital Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Bannas
authors.affiliation: Global MR Applications and Workflow, GE Healthcare, Madison, Wisconsin, USA.
authors.forename: James H
authors.initials: JH
authors.lastname: Holmes
authors.affiliation: Global MR Applications and Workflow, GE Healthcare, Madison, Wisconsin, USA.
authors.forename: Kang
authors.initials: K
authors.lastname: Wang
authors.affiliation: Global MR Applications and Workflow, GE Healthcare, Menlo Park, California, USA.
authors.forename: Ann
authors.initials: A
authors.lastname: Shimakawa
authors.affiliation: Global MR Applications and Workflow, GE Healthcare, Hino, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Iwadate
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Valentina
authors.initials: V
authors.lastname: Taviani
authors.affiliation: Department of Pediatrics, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Rehm
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin, USA.|Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.|Department of Biomedical Engineering and Medicine, 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: D005234:Fatty Liver / Q000473:pathology*; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011522:Protons; D015203:Reproducibility of Results
chemical_list: D011522:Protons
keywords: fat quantification; liver; magnetic resonance imaging; navigator echo; respiratory monitoring
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