Acoustic radiation force creep-recovery: theory and finite element modeling

Shear wave elasticity imaging methods have demonstrated that tissue elasticity changes with disease state. The majority of current methods use shear wave speed and rely on rheological models to estimate mechanical properties such as elasticity and viscosity. A method to quantify viscoelastic properties in a model-independent manner by using acoustic radiation force induced recovery is useful to estimate tissue mechanical properties independent of the applied force and fitting models. In this study the acoustic radiation force recovery theory is reviewed and it is tested in tissue mimicking phantoms. Moreover, a finite element model (FEM) is used to study the acoustic radiation force induced recovery strain under different conditions of material properties defined by Voigt model, density and geometry. From the FEM study it was found that the shear strain can be approximated as the partial derivative of vertical displacement with respect to lateral distance. Moreover, FEM and experimental data showed that recovery strain is more likely to converge to Voigt model when viscosity is high.