Time-resolved response of microbubble ultrasound contrast agents driven by traveling acoustic waves

Microbubble ultrasound contrast agents have been used for more than two decades in medical sonography to enhance the contrast between the blood pool and the surrounding tissue. Recently, such agents have been promoted as drug carriers for targeted drug administration mediated by ultrasound. Despite the progress achieved, a full understanding of the microbubble behavior that stimulates drug uptake is still lacking which hinders their translation to clinical practice. Our experimental studies are aimed at a detailed characterization of the translational, non-linear oscillation and clustering dynamics of ultrasound contrast agents. The microbubble dynamics, driven by MHz-frequency ultrasound, is recorded over a range of diameters and pressures through ultra-high-speed videomicroscopy imaging. Time-resolved experiments reveal the response of individual microbubbles and the distinct dynamical features of their interfaces. The results are compared with theoretical predictions and serve to gain further insights on the role of the encapsulating shell in the overall microbubble dynamics.