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ISSN Online: 2379-1748

ISBN Flash Drive: 978-1-56700-483-0

ISBN Online: 978-1-56700-482-3

4th Thermal and Fluids Engineering Conference
April, 14–17, 2019 , Las Vegas, NV, USA

Encapsulated microbubbles for contrast ultrasound imaging and drug delivery: from pressure dependent subharmonic to collapsing jet and acoustic streaming

Get access (open in a dialog) pages 817-828
DOI: 10.1615/TFEC2019.bio.028506

Abstract

Intravenously injected microbubbles used as ultrasound contrast enhancing agents are encapsulated by a nanometer-thick layer of lipids, proteins or polymers to stabilize them against premature dissolution. Over the years, we have developed interfacial rheological models for the encapsulation and used them to characterize several contrast agents by acoustic means. This is conducted in two directions. The first is on using subharmonic signals from the contrast microbubbles for non-invasive pressure estimation. Experimental measurement and modeling show that the subharmonic signal can both increase or decrease with pressure depending on frequency. Secondly, we will discuss boundary element (BEM) simulation of the collapse of an encapsulated microbubble forming a jet near a blood vessel wall as well as their repeated pulsation which gives rise to acoustic microstreaming. Different rheology models of the encapsulation have been rigorously implemented in the BEM formulation. We will discuss the resulting stresses due to microbubble collapse and acoustic streaming near the wall leading to sonoporation, ultrasound induced drug delivery and therapy.