Hepatic viscoelastic parameters measured with MR elastography: Correlations with quantitative analysis of liver fibrosis in the rat

Abstract

Purpose: To determine the correlations between the viscoelastic parameters of the liver measured with in vivo MR elastography and quantitative analysis of liver fibrosis. Materials and Methods: MR elastography of the liver was performed in 10 rats with hepatic fibrosis induced by intraperitoneal carbon tetrachloride (CCU) injections and five normal rats. Longitudinal waves of 200 MHz were transmitted into the liver with a mechanical transducer. Wave propagation into the liver was analyzed with a phase-locked spin-echo sequence at 1.5 T. The viscoelastic parameters, obtained with the Voigt model, were correlated with automatic image analysis of the flbrotic areas and with analysis of the hydroxyproline content of the liver. Results: Substantial correlations were observed between the shear viscoelastic parameters and the percentage of fibrosis at automatic image analysis (r = 0.7, P = 0.005 for the elasticity, and r = 0.8, P = 0.001 for the viscosity) and moderate correlations were seen between the shear viscoelastic parameters and the hydroxyproline content (r = 0.6, P = 0.016 for the elasticity and r = 0.5, P = 0.041 for the viscosity). Conclusion: The viscoelastic parameters of the liver measured with in vivo MR elastography correlate with quantitative analysis of liver fibrosis. These results suggest that MR elastography is a promising noninvasive method to quantify liver fibrosis. © 2007 Wiley-Liss, Inc.