Estimating shear wave speeds and shear viscosities with a viscoelastic time-domain method

Shear wave elastography generates shear waves with an acoustic radiation force to obtain estimates of the shear wave speed. Shear wave elastography often utilizes time-of-flight calculations that apply cross-correlations or time-to-peak methods to obtain estimates of the shear wave speed in the time-domain. However, these time-domain methods fail to consider the effect of dispersion caused by the shear viscosity, which can introduce substantial errors into estimates of the shear wave speed. To solve this problem, a new viscoelastic method for estimating shear wave parameters in the time-domain is introduced. The performance of the new method, which is applied to shear wave particle velocity waveforms, is established by evaluating a simulated three-dimensional viscoelastic Green's function model for shear waves in the time-domain. Results show that the new viscoelastic time-domain method is applicable to locations outside of the push beam region at the focal depth and throughout a two-dimensional plane. The results also indicate that estimates of the shear wave speed are either comparable to or significantly improved relative to values obtained from cross-correlations while simultaneously providing estimates of the shear viscosity in the time-domain.