title: Analysis of liver viscosity behavior as a function of multifrequency magnetic resonance elastography (MMRE) postprocessing.
abstract: OBJECTIVE
  To analyze the relevance of the viscosity measurement as a liver diagnostic marker.
  
  
  METHODS
  To determine the level of fibrosis, a Fibroscan test was performed on 40 subjects (10 healthy volunteers and 30 patients). Subsequently, multifrequency magnetic resonance elastography (MMRE) tests were made with a pneumatic driver at 60, 70, and 80 Hz. Phase images were analyzed with two different postprocessing methods, without (Method 1) and with (Method 2) the inversion algorithm (IA), using rheological models (Voigt, springpot) in order to characterize the viscoelastic properties (viscosity: η and elasticity: μ).
  
  
  RESULTS
  MRE cartography of the viscous tendency (G″MRE_M2 ) measured within the region of interest (ROI) of the liver increased as a function of the level of fibrosis. Similar results were also obtained for the viscosity (ηmodels_M1 ) calculated with a postprocessing without IA. However, the viscosity (ηmodels_M2 ) remained constant with the stage of fibrosis when the postprocessing was composed of an IA. The experimental (μMRE_M1 and G'MRE_M2 ) and rheological (μmodels_M2 and μmodels_M1 ) elasticities always increased with the level of fibrosis regardless of the postprocessing method.
  
  
  CONCLUSIONS
  The variation of the liver viscosity parameter as a function of postprocessing revealed that this parameter should be further investigated to demonstrate its relevance in clinical practice.
authors.affiliation: Université de Technologie de Compiègne, UMR CNRS 7338, BioMécanique et BioIngénierie, Compiègne, France.
authors.forename: Gwladys E
authors.initials: GE
authors.lastname: Leclerc
authors.forename: Fabrice
authors.initials: F
authors.lastname: Charleux
authors.forename: Ludovic
authors.initials: L
authors.lastname: Robert
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Ho Ba Tho
authors.forename: Colette
authors.initials: C
authors.lastname: Rhein
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Latrive
authors.forename: Sabine F
authors.initials: SF
authors.lastname: Bensamoun
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000473:pathology / Q000503:physiopathology*; D008103:Liver Cirrhosis / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014783:Viscosity; D055815:Young Adult
keywords: elasticity; liver fibrosis; multifrequency magnetic resonance elastography; rheological models; viscosity