Shear property characterization of viscoelastic media using vibrations induced by ultrasound radiation force

A method is proposed to estimate the shear properties of a viscoelastic medium by evaluating the vibration response of an embedded sphere. Radiation force generated by two interfering ultrasound beams is used to vibrate the sphere, at frequencies below 1 kHz. The motion of the sphere under multiple driving frequencies is measured by either laser or ultrasound technique. By fitting a theoretical model to these velocity spectrum measurements, the shear modulus and viscosity of the media are estimated. Experiment results in silicon oils and gel phantoms were in good agreement with the theory.