Wideband MRE and static mechanical indentation of human liver specimen: Sensitivity of viscoelastic constants to the alteration of tissue structure in hepatic fibrosis

Abstract Despite the success of elastography in grading hepatic fibrosis by stiffness related noninvasive markers the relationship between viscoelastic constants in the liver and tissue structure remains unclear. We therefore studied the mechanical properties of 16 human liver specimens with different degrees of fibrosis, inflammation and steatosis by wideband magnetic resonance elastography (MRE) and static indentation experiments providing the specimens׳ static Young׳s modulus ( E ), dynamic storage modulus ( G ′) and dynamic loss modulus ( G ″). A frequency-independent shear modulus μ and a powerlaw exponent α were obtained by fitting G ′ and G ″ using the two-parameter sprinpot model. The mechanical parameters were compared to the specimens׳ histology derived parameters such as degree of Fibrosis ( F ), inflammation score and fat score, amount of hydroxyproline (HYP) used for quantification of collagen, blood markers and presurgery in vivo function tests. The frequency averaged parameters G ′, G ″ and μ were significantly correlated with F ( G ′: R =0.762, G ″: R =0.830; μ : R =0.744; all P