4K-5 Shear Wave Velocity Estimation Using Acoustic Radiation Force Impulsive Excitation in Liver In Vivo

Acoustic radiation force can be used to mechanically excite tissue in remote, focused locations, and the tissue response can be monitored using ultrasonic correlation based methods. The speed with which the resulting shear waves propagate away from the focal region can be estimated and used to quantify the material shear modulus, as originally proposed by Sarvazyan et. al. (1998). This imaging approach has been implemented by Bercoff et. al. (2004), using a highly parallel custom ultrasound system, and Helmholtz reconstructions. We have developed a system that is implemented on a commercial scanner using 4:1 parallel processing, and a new algorithm for estimating shear wave speed, which does not require 2nd order temporal and spatial differentiation of displacement data. The method is robust and generates consistent measurements over multiple acquisitions. The goal of our work is to develop this system for the purpose of staging liver fibrosis. The method was used to measure elastic moduli of liver in vivo in healthy human volunteers, and in a rat model, and the moduli obtained with this method are consistent with those reported in the literature