Effect of high intensity focused ultrasound on platelet activation, aggregation and adhesion

High intensity focused ultrasound (HIFU) is being considered as a non-invasive method to halt internal bleeding, thus we investigated the capability of HIFU to produce `acoustic primary hemostasis,' including platelet activation, aggregation and adhesion to a collagen-coated surface. Various HIFU doses were applied to platelet rich plasma (PRP) with and without ultrasound contrast agents (UCA). Flow cytometry, laser aggregometry, conventional microscopy, environmental scanning electron microscopy (ESEM) and passive cavitation detection were used to quantify platelet activation, aggregation, adhesion and associated cavitation. Our results have shown that HIFU can cause platelets in a PRP sample to activate, aggregate and adhere to a collagen-coated surface. Furthermore, UCA (0.1% by volume) can enhance the platelet activity and increase the amount of cavitation induced by HIFU. HIFU exposure alone can cause platelet activity, but the addition of UCA increases the amount and rate of cavitation and platelet activity; therefore cavitation is a likely mechanism of HIFU induced platelet activity.