Ultrafast Feedback Control of Stable Cavitation Induced by Rapid Short-pulse Ultrasound

Stable cavitation (SC) of microbubbles (MBs) induced by ultrasound shows promising clinical applications. Rapid short-pulse (RaSP) ultrasound could extend the lifetime of the flowing microbubbles in the focal region, improving spatiotemporal distribution of cavitation activities and achieving desirable and controllable therapeutic outcomes. However, due to the influence of the acoustic wave on the microbubbles' stability, a decay of cavitation energy between pulses is inevitable, causing nonuniform temporal distribution of stable cavitation. This study developed a new controller based on proportional feedback control method to ultrafastly regulate the stable cavitation activities induced by RaSP ultrasound. RaSP sequence with fixed peak negative pressure (PNP) was firstly applied to non-circulating and circulating microbubbles to determine the target stable cavitation dose (SCD) and the temporal distribution of cavitation intensity. Under the proposed controller with 753 microseconds time consumption, SCD maintained at a relatively stable level. The regulated excitation voltages in the exposure time indicated that microbubble’ stability and number were decreasing. Finally, under the optimized proportional coefficient 7.5×10 ⁻⁸ V ⁻¹ . S ⁻¹ , stability ratio of 55.9% and concentration ratio of 0.75×10 ⁻¹² V ² . s indicated the temporal distribution of stable cavitation activities were significantly improved by the proposed controller.