title: A Pilot Comparative Study of Quantitative Ultrasound, Conventional Ultrasound, and MRI for Predicting Histology-Determined Steatosis Grade in Adult Nonalcoholic Fatty Liver Disease.
abstract: OBJECTIVE
  The purpose of this study is to explore the diagnostic performance of two investigational quantitative ultrasound (QUS) parameters, attenuation coefficient and backscatter coefficient, in comparison with conventional ultrasound (CUS) and MRI-estimated proton density fat fraction (PDFF) for predicting histology-confirmed steatosis grade in adults with nonalcoholic fatty liver disease (NAFLD).
  
  
  METHODS
  In this prospectively designed pilot study, 61 adults with histology-confirmed NAFLD were enrolled from September 2012 to February 2014. Subjects underwent QUS, CUS, and MRI examinations within 100 days of clinical-care liver biopsy. QUS parameters (attenuation coefficient and backscatter coefficient) were estimated using a reference phantom technique by two analysts independently. Three-point ordinal CUS scores intended to predict steatosis grade (1, 2, or 3) were generated independently by two radiologists on the basis of QUS features. PDFF was estimated using an advanced chemical shift-based MRI technique. Using histologic examination as the reference standard, ROC analysis was performed. Optimal attenuation coefficient, backscatter coefficient, and PDFF cutoff thresholds were identified, and the accuracy of attenuation coefficient, backscatter coefficient, PDFF, and CUS to predict steatosis grade was determined. Interobserver agreement for attenuation coefficient, backscatter coefficient, and CUS was analyzed.
  
  
  RESULTS
  CUS had 51.7% grading accuracy. The raw and cross-validated steatosis grading accuracies were 61.7% and 55.0%, respectively, for attenuation coefficient, 68.3% and 68.3% for backscatter coefficient, and 76.7% and 71.3% for MRI-estimated PDFF. Interobserver agreements were 53.3% for CUS (κ = 0.61), 90.0% for attenuation coefficient (κ = 0.87), and 71.7% for backscatter coefficient (κ = 0.82) (p < 0.0001 for all).
  
  
  CONCLUSIONS
  Preliminary observations suggest that QUS parameters may be more accurate and provide higher interobserver agreement than CUS for predicting hepatic steatosis grade in patients with NAFLD.
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Paige
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Bernstein
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: Elhamy
authors.initials: E
authors.lastname: Heba
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: Eduardo A C
authors.initials: EAC
authors.lastname: Costa
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: Marilia
authors.initials: M
authors.lastname: Fereirra
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.|2 Computational and Applied Statistics Laboratory, University of California San Diego, San Diego, CA.
authors.forename: Tanya
authors.initials: T
authors.lastname: Wolfson
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.|2 Computational and Applied Statistics Laboratory, University of California San Diego, San Diego, CA.
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Gamst
authors.affiliation: 3 Department of Pathology, University of California San Diego, San Diego, CA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Valasek
authors.affiliation: 3 Department of Pathology, University of California San Diego, San Diego, CA.
authors.forename: Grace Y
authors.initials: GY
authors.lastname: Lin
authors.affiliation: 4 Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL.
authors.forename: Aiguo
authors.initials: A
authors.lastname: Han
authors.affiliation: 5 Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL.
authors.forename: John W
authors.initials: JW
authors.lastname: Erdman
authors.affiliation: 4 Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL.
authors.forename: William D
authors.initials: WD
authors.lastname: O'Brien
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.|6 San Diego VA Healthcare System, San Diego, CA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Andre
authors.affiliation: 7 NAFLD Translational Research Unit, Division of Gastroenterology, University of California San Diego, San Diego, CA.|8 Division of Epidemiology, Department of Family and Preventive Medicine, University of California San Diego, San Diego, CA.
authors.forename: Rohit
authors.initials: R
authors.lastname: Loomba
authors.affiliation: 1 Liver Imaging Group, Department of Radiology, University of California San Diego, 408 Dickinson St, San Diego, CA 92103-8226.
authors.forename: Claude B
authors.initials: CB
authors.lastname: Sirlin
mesh_terms: D000328:Adult; D000368:Aged; D001706:Biopsy; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011446:Prospective Studies; D014463:Ultrasonography / Q000379:methods*
keywords: attenuation; backscatter; grading accuracy; interobserver agreement; nonalcoholic fatty liver disease; nonalcoholic steatohepatitis; proton density fat fraction; quantitative imaging biomarkers; quantitative ultrasound