In the past decade acoustic radiation force became a powerful tool in numerous biomedical applications. Radiation force from a focused ultrasound beam acts as a virtual "finger" for remote probing of internal anatomical structures and obtaining diagnostic information. This presentation deals with generation of shear waves by nonlinear focused beams. Albeit the radiation force has intrinsically nonlinear origin, in most cases the motions generated by primary ultrasonic wave are considered in the linear approximation. In this presentation, we consider the effects of nonlinearly distorted beams on generation of shear waves in fluids, as well as nonlinearity in acoustic flows generated by such beams. The use of nonlinearly distorted, focused ultrasonic beams for enhancing radiation force and generation of shear waves in fluids, including biological tissues is discussed. It is shown that the shear displacement sharply increases near the focus even at a moderate nonlinear distortion.
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