Shear wave viscoelasticity imaging using local system identification

Tissue elasticity is an important parameter which relates to the pathological state of soft tissue. Fibrotic lesions or malignant tumors are known to be notoriously stiff compared to benign tissue. Shear wave elastography can provide a fully quantitative measure of lesion stiffness by estimating the speed at which acoustically induced shear waves propagate through the material. This speed is in turn related to the Young's modulus. In soft tissue, elasticity is generally accompanied by viscosity, leading to dispersion of the shear wave. For the detection and characterization of malignant lesions, viscosity has in fact diagnostic value. Here, we describe a new method that enables imaging not only elasticity but also viscosity from shear wave elastography by local model-based system identification. We show that the proposed method can be applied effectively to standard shear wave acquisitions, and is able to generate high-resolution parametric maps of the viscoelastic material properties in an in-vitro setting.