title: Accuracy of Liver Fat Quantification With Advanced CT, MRI, and Ultrasound Techniques: Prospective Comparison With MR Spectroscopy.
abstract: OBJECTIVE
  The purpose of this study was to prospectively evaluate the accuracy of proton-density fat-fraction, single- and dual-energy CT (SECT and DECT), gray-scale ultrasound (US), and US shear-wave elastography (US-SWE) in the quantification of hepatic steatosis with MR spectroscopy (MRS) as the reference standard.
  
  
  METHODS
  Fifty adults who did not have symptoms (23 men, 27 women; mean age, 57 ± 5 years; body mass index, 27 ± 5) underwent liver imaging with un-enhanced SECT, DECT, gray-scale US, US-SWE, proton-density fat-fraction MRI, and MRS for this prospective trial. MRS voxels for the reference standard were colocalized with all other modalities under investigation. For SECT (120 kVp), attenuation values were recorded. For rapid-switching DECT (80/140 kVp), monochromatic images (70-140 keV) and fat density-derived material decomposition images were reconstructed. For proton-density fat fraction MRI, a quantitative chemical shift-encoded method was used. For US, echogenicity was evaluated on a qualitative 0-3 scale. Quantitative US shear-wave velocities were also recorded. Data were analyzed by linear regression for each technique compared with MRS.
  
  
  RESULTS
  There was excellent correlation between MRS and both proton-density fat-fraction MRI (r2= 0.992; slope, 0.974; intercept, -0.943) and SECT (r2= 0.856; slope, -0.559; intercept, 35.418). DECT fat attenuation had moderate correlation with MRS measurements (r2= 0.423; slope, 0.034; intercept, 8.459). There was good correlation between qualitative US echogenicity and MRS measurements with a weighted kappa value of 0.82. US-SWE velocity did not have reliable correlation with MRS measurements (r2= 0.004; slope, 0.069; intercept, 6.168).
  
  
  CONCLUSIONS
  Quantitative MRI proton-density fat fraction and SECT fat attenuation have excellent linear correlation with MRS measurements and can serve as accurate noninvasive biomarkers for quantifying steatosis. Material decomposition with DECT does not improve the accuracy of fat quantification over conventional SECT attenuation. US-SWE has poor accuracy for liver fat quantification.
authors.affiliation: 1 Department of Clinical Radiology, University Hospitals Munich, Ludwig Maximilians University, Marchioninistr 15, 81377 Munich, Germany.|2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.
authors.forename: Harald
authors.initials: H
authors.lastname: Kramer
authors.affiliation: 2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
authors.affiliation: 2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kliewer
authors.affiliation: 2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.
authors.forename: Diego
authors.initials: D
authors.lastname: Hernando
authors.affiliation: 2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.|3 Department of Medical Physics, University of Wisconsin-Madison, Madison, WI.
authors.forename: Guang-Hong
authors.initials: GH
authors.lastname: Chen
authors.affiliation: 2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.|3 Department of Medical Physics, University of Wisconsin-Madison, Madison, WI.
authors.forename: James A
authors.initials: JA
authors.lastname: Zagzebski
authors.affiliation: 2 Department of Radiology, University of Wisconsin-Madison, Madison, WI.|3 Department of Medical Physics, University of Wisconsin-Madison, Madison, WI.|4 Departments of Biomedical Engineering, Medicine, and Emergency Medicine, University of Wisconsin-Madison, Madison, WI.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
mesh_terms: D050154:Adiposity / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D050152:Intra-Abdominal Fat / Q000000981:diagnostic imaging / Q000502:physiology*; D008099:Liver / Q000000981:diagnostic imaging / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT; MR spectroscopy; MRI; fat quantification; hepatic steatosis; ultrasound