Dissolved oxygen scavenging by acoustic droplet vaporization using intravascular ultrasound

Modification of dissolved gas content by acoustic droplet vaporization (ADV) has been proposed for several therapeutic applications. Reducing dissolved oxygen (DO) during reperfusion of ischemic tissue during coronary interventions could inhibit reactive oxygen species production and rescue myocardium. The objective of this study was to determine whether intravascular ultrasound (IVUS) can trigger ADV and reduce DO. Perfluoropentane emulsions were created using highspeed shaking and microfluidic manufacturing. High-speed shaking resulted in a polydisperse droplet distribution ranging from less than 1 micron to greater than 16 microns in diameter. Microfluidic manufacturing produced a narrower size range of droplets with diameters between 8.0 microns and 9.6 microns. The DO content of the fluids was measured before and after ADV triggered by IVUS exposure. Duplex B-mode and passive cavitation imaging was performed to assess nucleation of ADV. An increase in echogenicity indicative of ADV was observed after exposure with a clinical IVUS system. In a flow phantom, a 20% decrease in DO was measured distal to the IVUS transducer when droplets, formed via high-speed shaking, were infused. In a static fluid system, the DO content was reduced by 11% when droplets manufactured with a microfluidic chip were exposed to IVUS. These results demonstrate that a reduction of DO by ADV is feasible using a clinical IVUS system. Future studies will assess the potential therapeutic efficacy of IVUS-nucleated ADV and methods to increase the magnitude of DO scavenging.