Role of high intensity focused ultrasound induced cavitation on platelet aggregation

Abstract

Our previous studies showed that high-intensity focused ultrasound (HIFU) is capable of producing ‘‘primary acoustic hemostasis’’ in the form of platelet activation, aggregation, and adhesion to a collagen-coated surface. In current studies, 1.1 MHz CW HIFU was used to investigate the role of cavitation as a mechanism for platelet aggregation in samples of platelet rich plasma. A 5 MHz passive cavitation detector was used to monitor cavitation activity, and laser aggregometry was used to measure platelet aggregation. Using spatial average intensities from 0 to 4000 W/cm2, the effects of HIFU induced cavitation on platelet aggregation were investigated by enhancing cavitation activity through use of ultrasound contrast agents, and by limiting cavitation activity through use of an overpressure system. Our results show that increased cavitation activity lowers the intensity threshold to produce platelet aggregation, and decreased cavitation activity in the overpressure system raises the intensity threshold for platelet aggregation. [Research supported by DARPA.]