Measurement of shear wave absorption with correction of the diffraction effect for viscoelasticity characterization of soft tissues

An ultrasonic method for measuring shear wave (SW) propagation properties in soft tissues was investigated for viscoelasticity characterization. A continuous SW was induced into a specimen by an external vibration source. The displacements within the specimen due to the SW propagation were measured by a speckle-echo tracking method using a conventional B-mode scan of focused ultrasound. SW velocity and absorption coefficient of the specimen were retrieved from the measured SW waveforms with the compensation of the SW diffraction. The effect of positioning error of the ultrasound probe on the diffraction calculation was studied by numerical simulations. It was shown that the estimation error of the SW absorption could be reduced by selecting an appropriate SW measurement region where the diffraction estimation precision is less sensitive to the positioning error of the probe. Finally, the shear elasticity and viscosity of a soft tissue mimicking phantom were estimated.