Extending the Iterative Nonlinear Contrast Source method to simulate mutual interaction in large populations of microbubbles

Abstract

There is an ongoing development of ultrasound contrast agents (UCAs) for specific medical diagnostic and therapeutic applications. Recent researches involve all kinds of targeted and loaded microbubbles, monodisperse microbubbles, and phase-change nanodroplets. To design and improve applications that use UCAs, it is necessary to have a thorough understanding of the mutual interaction of ultrasound fields and UCAs. The individual response of microbubbles and nanodroplets is extensively studied and, in the case of bubbles, multiple variants of the Rayleigh-Plesset equation are available to describe their behavior. However, novel applications, such as therapeutic proton beam localization, may strongly depend on the mutual interaction in a population of UCAs. In this presentation, a numerical approach for the analysis of ultrasound-bubble interaction in a population with many (order one million) microbubbles will be discussed. This approach is based on the earlier developed Iterative Nonlinear Contrast Source (INCS) method for simulating nonlinear ultrasound waves. In the current case, the population of microbubbles will be represented by a set of pressure-dependent contrast point sources that are iteratively updated by the INCS method, where each iteration adds an order of multiple scattering. Results will be presented for the linear scattering in populations with different concentrations of microbubbles.