Assessment of the Solid-Liquid Behavior of the Liver for the Diagnosis of Diffuse Disease Using Magnetic Resonance Elastography

Purpose: Recent magnetic resonance elastography (MRE) studies have reported the potential of this noninvasive method for diagnosing hepatic fibrosis based on the elastic properties of liver tissue. However, in many cases biological tissue responds to mechanical vibrations as a combined solid-liquid body causing MRE-derived elastic parameters to become functions of the applied vibration frequency. Therefore a multi-frequency MRE Study of liver was performed and the potential of the method for separating healthy from fibrotic liver was investigated. The aim of this study was the increase of the accuracy of liver elastography by analyzing multi-frequency MRE examinations using the springpot model. Materials and Methods: 18 healthy volunteers and 10 patients were examined by multi-frequency MRE of the liver in a frequency range between 25 Hz and 62.5 Hz. The liver was mechanically excited with four harmonic vibrations simultaneously. The measured dispersion of the complex modulus was analyzed using the springpot model which accounts for both elastic and viscous properties of a material with 2 independent parameters. Results: The mechanical stimulation and the motion encoding according to the multi-frequency approach was implemented successfully. Significant differences (p < 0.05) were found in the hepatic viscoelasticities of normal livers. The separation of healthy volunteers and patients was achieved with a sensitivity and specificity of 80 and 100%, respectively. Conclusion: Using the springpot model, multi-frequency MRE is sensitive to interindividual differences in the hepatic viscoelastic properties of healthy volunteers. The obtained accuracy of the technique in separating healthy from fibrotic livers opens the possibility of applying multi-frequency MRE as a noninvasive method for diagnosing liver fibrosis in the future.