Abstract: Harmonic motion is produced in a subject using vibro-acoustography. An ultrasonic imaging system repetitively interrogates the subject and the Doppler shift in the reflected echo signals is analyzed to measure the phase and amplitude of harmonic motion produced in the subject at different prescribed frequencies. Shear wave propagation through the subject is determined from this information and mechanical properties related to “stiffness” of the subject are determined. A Kalman filter is employed in the phase and amplitude measurement to extract the harmonic motion information from background noise.

Abstract: A method for determining a shear elasticity and shear viscosity of a material based on resonance characteristics. A focused ultrasound wave is directed at the material to induce oscillations in the material, and a velocity of the material is measured. A spectrum of frequency of oscillation versus velocity is developed, and the resonance characteristics exhibited by the spectrum are used to estimate the shear elasticity and viscosity of the material.