Control of nonlinear bubble dynamics

Abstract

Bubbles, either free or encapsulated, are valuable as contrast agents in diagnostic ultrasound in medicine. In this capacity, the compressibility of microbubbles is exploited to increase the acoustic backscatter from internal vessels and cavities of interest after injection into the patient. The scattering cross section of the contrast agent is further increased by driving resonant radial pulsations of the microbubbles with the ultrasound field. Recent derivatives of this basic technique rely on nonlinear aspects of the bubble response to reduce clutter and thereby to extend imaging capability to new areas. Unlike the surrounding tissue, these nonlinear bubble oscillations have a backscatter signature at a different frequency than the forcing, and so are especially useful in distinguishing the area to be imaged. New control capabilities are described for changing the architecture of the bubble dynamics phase portrait and response diagram so as to enhance their utility in imaging applications. [Work supported by NSF.]