Shear-Modulus Estimation by Application of Spatially Modulated Impulse Acoustic Radiation Force Approximation

Abstract

A method for determining a shear modulus of an elastic material with a known density value is provided. In this method, a spatially modulated acoustic radiation force is used to initially generate a disturbance of known spatial frequency or wavelength. The propagation of this initial displacement as a shear wave is measured using ultrasound tracking methods. A temporal frequency is determined based on the shear wave. The shear modulus of the elastic material at the point of excitation may be calculated using the values of the spatial wavelength, material density, and temporal frequency.

What is claimed is: 
     
         1 . A method for determining a speed of a shear wave in a material, comprising the steps of:
 applying a disturbance having a known wavelength to the material to cause a shear wave to be produced in the material;   measuring a temporal frequency of the shear wave; and   calculating the speed of the shear wave by using the measured temporal frequency of the shear wave and the known wavelength of the disturbance.   
     
     
         2 . The method of  claim 1 , wherein the material comprises human or animal soft tissues. 
     
     
         3 . The method of  claim 1 , wherein the step of applying the disturbance having the known wavelength comprises using an acoustic radiation force impulse to generate the disturbance. 
     
     
         4 . The method of  claim 1 , further comprising the steps of:
 applying one or more additional disturbances to the material to cause one or more shear waves corresponding to each of the one or more additional disturbances, wherein each of the one or more additional disturbances has a known wavelength which is different than that of the disturbance and other of the one or more additional disturbances;   measuring a temporal frequency of each of the corresponding shear waves; and   calculating the speed of each of the corresponding shear waves at each of the measured temporal frequencies by using the known wavelength of each of the one or more additional disturbances and the measured temporal frequency of the corresponding shear wave.   
     
     
         5 . The method of  claim 1 , further comprising the steps of:
 calculating a shear modulus of the material using the calculated speed of the shear wave, known density of the material, and the known wavelength of the disturbance; and   providing the shear modulus as an output.