Motion of spherical microparticles in a viscoelastic medium under the action of acoustic radiation force

The motion of spherical microparticles with sizes (50–250 μm) less than or comparable to the wavelength of ultrasound (300 μm) in a gel-like medium is studied. Particle displacement is defined by the acoustic radiation force and the motion of the medium. It is shown that a specific feature of microparticle motion is their complete deceleration for a time of about 1 ms after switching off the ultrasound, and their subsequent displacement is determined entirely by the medium’s relaxation. The aim of the work is to develop ultrasonic means of detecting microcalcifications in breast tissues.