Nonlinear response of encapsulated contrast microbubbles for noninvasive blood pressure measurement

George Washington University, Washington DC

Investigators

Abstract

CBET - 1603639 PI: Sarkar, Kausik Microbubbles are used routinely in medical diagnostics to enhance the contrast of ultrasound images. The microbubbles usually are encapsulated with lipids or proteins so that they persist when introduced into the blood stream. The hypothesis of this project is that the acoustic response of encapsulated microbubbles in the bloodstream can be separated from the acoustic response of surrounding tissue and can be used to measure the blood pressure in the small blood vessels of various organs. The project comprises experiments to measure the acoustic response of encapsulated microbubbles under varying ambient pressures, the development of a numerical model to help interpret the experimental data, and the formulation of a protocol for pressure estimation that will be tested in collaboration with physicians at Thomas Jefferson University who discovered that the acoustic response of encapsulated microbubbles depends on the local pressure. Results of the study could provide physicians with a new diagnostic tool to measure blood pressure throughout the body to enable early detection of disease in specific organs. The investigators will involve in the project students at all academic levels, including undergraduates from groups traditionally underrepresented in science and engineering. This proposal builds on an observation made by clinicians at the Thomas Jefferson University that the subharmonic response from contrast microbubbles decreases with increasing ambient pressure. However, other experiments, including those by the project investigators, and models developed by the investigators suggest the subharmonic response may increase or decrease with ambient pressure. The goal of the project is to explain the apparent discrepancy, delineate regions of different behaviors, and determine how the subharmonic response depends on the pressure-dependent mechanical properties of encapsulated microbubbles. In collaboration with clinicians at Thomas Jefferson Medical Hospital, the investigators will synthesize lipid coated microbubbles and characterize their encapsulations using a nonlinear interfacial rheological model at different ambient pressures, investigate the pressure dependent nonlinear response from contrast microbubbles, and determine optimal material and excitation parameters for pressure estimation.