title: Derivation and analysis of viscoelastic properties in human liver: impact of frequency on fibrosis and steatosis staging.
abstract: Commercially-available shear wave imaging systems measure group shear wave speed (SWS) and often report stiffness parameters applying purely elastic material models. Soft tissues, however, are viscoelastic, and higher-order material models are necessary to characterize the dispersion associated with broadband shear waves. In this paper, we describe a robust, model-based algorithm and use a linear dispersion model to perform shear wave dispersion analysis in traditionally difficult-to-image subjects. In a cohort of 135 non-alcoholic fatty liver disease patients, we compare the performance of group SWS with dispersion analysis-derived phase velocity c(200 Hz) and dispersion slope dc/df parameters to stage hepatic fibrosis and steatosis. Area under the ROC curve (AUROC) analysis demonstrates correlation between all parameters [group SWS, c(200 Hz), and, to a lesser extent dc/df ] and fibrosis stage, whereas no correlation was observed between steatosis stage and any of the material parameters. Interestingly, optimal AUROC threshold SWS values separating advanced liver fibrosis (≥F3) from mild-to-moderate fibrosis (≤F2) were shown to be frequency-dependent, and to increase from 1.8 to 3.3 m/s over the 0 to 400 Hz shear wave frequency range.
authors.forename: Kathryn R
authors.initials: KR
authors.lastname: Nightingale
authors.forename: Ned C
authors.initials: NC
authors.lastname: Rouze
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Rosenzweig
authors.forename: Michael H
authors.initials: MH
authors.lastname: Wang
authors.forename: Manal F
authors.initials: MF
authors.lastname: Abdelmalek
authors.forename: Cynthia D
authors.initials: CD
authors.lastname: Guy
authors.forename: Mark L
authors.initials: ML
authors.lastname: Palmeri
mesh_terms: D000465:Algorithms; D004548:Elasticity / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005234:Fatty Liver / Q000000981:diagnostic imaging / Q000503:physiopathology*; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000000981:diagnostic imaging / Q000502:physiology*; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012372:ROC Curve