Devices, Methods, and Systems for Measuring Elastic Properties of Biological Tissues Using Acoustic Force

Abstract

A device, method, and system for using an acoustic radiation force resulting from focused ultrasound energy in order to generate an internal force remotely and to measure quantitatively tissue elasticity in vivo and non-invasively.

1 . A method for measuring elasticity within a tissue volume, comprising:
 emitting ultrasound radiation force from a contact region of a surface of a tissue volume energy to vibrate focal region remote from the surface;   generating image data representing at least a portion of the focal region and a region surrounding the focal region;   from image data resulting from the imaging, extracting displacement magnitude data characterizing the vibration of the focal region;   determining a net force causing the focal region vibration;   calculating an elastic property of the tissue volume within the immediate vicinity of the focal region from the net force and the displacement data.   
     
     
         2 . The method of  claim 1 , wherein the calculating depends on a relationship between strain and the elastic property. 
     
     
         3 . The method of  claim 1 , wherein the calculating includes calculating an elastic property responsively to displacement data representing a magnitude of deformation of portions of the tissue volume at multiple locations on the boundaries of the focal region. 
     
     
         4 . The method of  claim 1 , wherein the extracting includes determining displacements at multiple locations along lines running toward and away from the focal region. 
     
     
         5 . The method of  claim 1 , wherein the focal region is an approximately cylindrical volume, and the calculating accounts separately for shear and compression deformation of the tissue volume. 
     
     
         6 . The method of  claim 1 , wherein the generating the image data is performed at the same time as the emitting such that motion is directly caused by the radiation force. 
     
     
         7 . The method of  claim 6 , wherein the ultrasound radiation force is generated by modulating a transducer power output at a frequency in a range of 10-500 Hz. 
     
     
         8 - 76 . (canceled) 
     
     
         77 . A method for quantitative measurement of an elasticity parameter of a target location within a subject, comprising:
 applying remotely an amplitude-modulated ultrasound energy at a focal region of the target location to modulate the focal region   at a predetermined frequency   and exert a predetermined acoustic force on a region of the target location surrounding the focal region;   simultaneously acquiring a sequence of images of the region surrounding the focal region, the images representing the axial movement of the region due to the exertion of the acoustic force on the region;   determining an axial displacement of the region from the sequence of images using cross-correlation; and   calculating an elasticity parameter based on a relationship between the elasticity parameter, the axial displacement, and the predetermined acoustic force,   wherein the elasticity parameter is an elastic modulus.   
     
     
         78 . The method of  claim 77 , wherein the calculating further includes calculating spatial derivatives of the axial displacement. 
     
     
         79 . The method of  claim 77 , wherein the target location is a biological tissue and/or organ located within a living subject. 
     
     
         80 . The method of  claim 77 , further comprising comparing the calculated elastic modulus with a known elastic modulus. 
     
     
         81 . The method of  claim 78 , further comprising moving the focused ultrasound energy to scan its focal point over a region in the sample to be imaged and applying the acoustic force at different target locations, measuring at each location the axial displacement of the target location due to the applied acoustic force, and determining the mechanical property of the sample at different target locations. 
     
     
         82 . The method of  claim 81 , further comprising generating a map of the measured mechanical property of the sample at different target locations. 
     
     
         83 . The method of  claim 81 , further comprising changing the modulation frequency of the focused ultrasound energy during the scanning over a range of values. 
     
     
         84 . The method of  claim 83 , wherein the frequency range is between 10-1000 Hz. 
     
     
         85 . A method for detecting tumors in a sample tissue of a living subject, comprising:
 causing an internal deformation of the sample tissue by applying remotely an amplitude-modulated oscillating acoustic force at a target location within the tissue;   simultaneously measuring the axial and the shear strains in the tissue caused by the applied acoustic force;   calculating the elasticity modulus of the tissue based on the measured axial and shear strains and the known acoustic force;   responsively to the elasticity, repeating said causing at a different frequency.   
     
     
         86 . The method of  claim 85 , further comprising:
 moving a focused ultrasound energy to scan its focal point over a region in the sample tissue to be imaged and applying the acoustic force at different target locations;   measuring at each location the axial and shear strains;   determining the elastic modulus of the tissue at different target locations within the sample tissue; and   mapping the elasticity of the sample at different target locations based on the determined elastic modulus.