Shear Wave Dispersion in Chronic Liver Disease: From Physical Principles to Clinical Usefulness

Abstract

The development of new applications in ultrasound (US) imaging in recent years has strengthened the role of this imaging technique in the management of different pathologies, particularly in the setting of liver disease. Improved B-mode imaging (3D and 4D), contrast-enhanced US (CEUS) and especially US-based elastography techniques have created the concept of multiparametric ultrasound (MP-US), a term borrowed from radiological sectional imaging. Among the new elastography techniques, shear wave dispersion is a newly developed imaging technology which enables the assessment of the shear waves' dispersion slope. The analysis of the dispersion qualities of shear waves might be indirectly related to the tissue viscosity, thus providing biomechanical information concerning the pathologic state of the liver such as necroinflammation. Some of the most recent US devices have been embedded with software that evaluate the dispersion of shear waves/liver viscosity. In this review, the feasibility and the clinical applications of liver viscosity are reviewed based on the preliminary findings of both animal and human studies.

Keywords: chronic liver disease; elastography; fibrosis; inflammation; multiparametric ultrasound; share wave dispersion; steatosis; viscosity.

Figure 1

Variability of shear wave viscosity, frequency, and dispersion slope in viscoelastic medium.

Figure 2

An example of 2D-SWE (upper part of the image) and viscosity (lower part of the image) in a patient with clinically significant liver fibrosis (F2) and mild inflammation (A1) measured with SSI using the Vi.Plus software.