Spectral peak suppression in the acoustic emissions from multiple microbubbles cavitating in focused ultrasound

Non-linear acoustic emissions from contrast agent microbubbles under focused ultrasound exposure, are often used to monitor therapeutic efficacy, and avoid long term tissue damage. We have recently reported on the mechanistic source for non-linear emissions as periodic bubble-collapse generated shock waves. In this proceeding we present a dual perspective high-speed imaging with parallel acoustic detection dataset, for the cavitation initiated from two microbubbles exposed to focused ultrasound of f
₀
= 692 kHz at peak-negative pressure amplitude of 1.14 MPa. Both cavitation-bubble clouds respond in the period doubled, f
₀
/2 subharmonic shock emission regime. The cloud collapses, however, are out of phase with respect to each other, such that shocks are detected at the hydrophone at f
₀
. We demonstrate peak suppression in the spectrum of the combined emissions, at key frequency values.