Phase velocity dispersion estimation of viscoelastic materials by two-point wavelet-based method

Abstract

Ultrasound shear wave elastography (SWE) is a promising imaging modality used for noninvasive, quantitative evaluation of tissue mechanical properties. This method uses an acoustic radiation force to produce laterally propagating shear waves that can be tracked to obtain the wave velocity. One of the ways to explore the viscoelasticity is through examining the shear wave velocity dispersion curves. In this paper, we present an alternative method to the classical two-dimensional Fourier transform (2D-FT), a two-point wavelet transformation method. We use the Morlet wavelet function as the mother wavelet to filter two shear waves at different locations. We examined how starting distance from the push and distance between the two locations affected the shear wave velocity dispersion. We tested this method on digital phantom data created using local interaction simulation approach (LISA) in viscoelastic media and on data acquired from phantom experiments. We compared results from the two-point method with the 2D-FT technique. The two-point method provided dispersion curves estimation with lower errors over a wider frequency band. Tests conducted showed that the two-point technique gives results with better accuracy in simulation results and can be used to measure phase velocity of viscoelastic materials.