Ultrasonic microstreaming and related phenomena.

It has been shown in recent work that biological cells and tissues are affected by low intensity ultrasound in the lower megahertz frequency range if small gas-filled channels or pores are present, with dimensions in the range of a few microns. When these gas bodies pulsate in response to the ultrasound they act on surrounding media by unique forms of radiation pressure, forces and torque; in liquids small-scale eddying is generated, known as microstreaming. It is probably by combinations of these phenomena that biological effects are produced.