Accounting for the stability of microbubbles to multi-pulse excitation using a lipid-shedding model

Interest in microbubble ultrasound contrast agents as therapeutic and quantitative imaging tools has increased the need for accurate modeling of their behavior. Experiments have shown that some bubbles shrink significantly over the course of a single pulse but that the bubbles may eventually reach a stable size after many insonations. Here, it is shown from dimensional arguments that diffusion phenomena are negligible on the time scales that characterize a typical ultrasound pulse. Subsequently, a new model describing both a lipid-shedding mechanism and a nonlinear surface viscosity is developed and shown to provide a more accurate description of the observed experimental behavior.