Acoustic cavitation series: part six. Gas body activation.

A small body of gas which is stabilized against dissolution in a liquid by a supportive structure may oscillate in response to an ultrasonic field and this form of cavitation is termed gas body activation. Linear theory describes the response of gas-filled intercellular channels in plant tissue and of gas-filled micropores in thin sheets of plastic. Calculations from this theory yield good agreement with indirect observations of resonance frequencies and rough agreement with direct measures of aggregate response (transmission and reflection coefficients). Studies of gas body activation in biological systems should allow quantitative analysis of cavitation bioeffects for relatively low-intensity ultrasound applications.