Numerical study on growth and collapse of cloud cavitation in a focused ultrasound field

Abstract

Acoustic cavitation is becoming increasingly important in therapeutic ultrasound applications. Nonlinear behavior as well as spatial distribution of cloud cavitation in a focused ultrasound field needs to be clarified to enhance the mechanical effects of cavitation on treatments such as lithotripsy and histotripsy. For this purpose, an ultrasound simulator treating cavitation has been developing. Since the distribution of the cloud cavitation generated in a focused ultrasound field results from the complex interactions between bubble oscillation and ultrasound, the bubble oscillation is strongly coupled with the focused ultrasound field. In addition, rectified diffusion, which plays an important role in the cavitation bubble growth, is taken into account. A focused ultrasound lithotripsy using the collapse of cloud cavitation was demonstrated numerically. The cloud cavitation is generated by the high frequency ultrasound waves and is collapsed by the low frequency ultrasound waves. As the result of the simulation, the cavitation bubble growth from nuclei around focus region in front of the model stone were reproduced. Then, the collapse of the cloud cavitation caused high pressure on the surface of the stone.Acoustic cavitation is becoming increasingly important in therapeutic ultrasound applications. Nonlinear behavior as well as spatial distribution of cloud cavitation in a focused ultrasound field needs to be clarified to enhance the mechanical effects of cavitation on treatments such as lithotripsy and histotripsy. For this purpose, an ultrasound simulator treating cavitation has been developing. Since the distribution of the cloud cavitation generated in a focused ultrasound field results from the complex interactions between bubble oscillation and ultrasound, the bubble oscillation is strongly coupled with the focused ultrasound field. In addition, rectified diffusion, which plays an important role in the cavitation bubble growth, is taken into account. A focused ultrasound lithotripsy using the collapse of cloud cavitation was demonstrated numerically. The cloud cavitation is generated by the high frequency ultrasound waves and is collapsed by the low frequency ultrasound waves. As the result of the si...