Viscoelastic properties of liver measured by oscillatory rheometry and multifrequency magnetic resonance elastography.

The mechanical properties of liver can sensitively indicate the progression of hepatic fibrosis. Mechanical tissue characterization involves the analysis of the complex shear modulus measured either by oscillatory rheometry or by in vivo elastography. In this study, bovine liver specimens were investigated by oscillatory rheometry and multifrequency magnetic resonance elastography (MRE) in a common frequency range between 25.0 and 62.5 Hz. The results were compared with in vivo MRE of human liver. Storage and loss moduli were quantified, and the data were also analyzed employing a springpot model, yielding a stiffness-related parameter of 2.96+/-0.53 kPa in bovine liver by rheometry and of 2.20+/-0.45 kPa in human liver by in vivo MRE. Furthermore, MRE of excised bovine liver showed that stiffness tended to increase with decreasing sample temperature. In conclusion, mechanical tissue characterization by multifrequency MRE agrees well with oscillatory rheometry, which validates MRE as a method for investigating the rheology of liver tissue.