Interfacial Rheological Properties of Contrast Microbubble Targestar P as a Function of Ambient Pressure

Abstract

In this Technical Note, we determine the interfacial rheological parameters of the encapsulation of the contrast agent Targestar P using ultrasound attenuation. The characteristic parameters are obtained according to two interfacial rheological models. The properties-surface dilatational elasticity (0.09 ± 0.01 N/m) and surface dilatational viscosity (8 ± 0.1E-9 N·s/m)-are found to be of similar magnitude for both models. Contrast microbubbles experience different ambient pressure in different organs. We also measure these parameters as functions of ambient pressure using attenuation measured at different overpressures (0, 100 and 200 mm Hg). For each value of ambient hydrostatic pressure, we determine the rheological properties, accounting for changes in the size distribution caused by the pressure change. We discuss different models of size distribution change under overpressure: pure adiabatic compression or gas exchange with surrounding medium. The dilatational surface elasticity and viscosity are found to increase with increasing ambient pressure.

High-precision acoustic measurements of the nonlinear dilatational elasticity of phospholipid coated monodisperse microbubbles

“…48,49 Furthermore, motivated by in-vivo blood pressure variations, Kumar et al measured shell properties at overpressures up to 200 mm Hg (27 kPa). 50 For Definity bubbles with a very similar shell composition to the 10% PEG lipid mixture used here, Kumar et al 51 also found a shell viscosity and shell elasticity increase for increased ambient pressures.…”

Acoustic microstreaming near a plane wall due to a pulsating free or coated bubble: velocity, vorticity and closed streamlines

“…We have shown that different models of coating often give rise to qualitatively similar behaviours (Kumar & Sarkar 2015; Xia et al. 2015; Kumar & Sarkar 2016) even for nonlinear response. We expect that they would vary very little in their predictions of linear dynamics.…”

“…where We s b = ρR 3 0 ω 2 /E s 0 , Re s b = ρR 3 0 ω/κ s , γ 0 /E s 0 and α s are the non-dimensional numbers related to the coating parameters. We have shown that different models of coating often give rise to qualitatively similar behaviours (Kumar & Sarkar 2015;Xia et al 2015;Kumar & Sarkar 2016) even for nonlinear response. We expect that they would vary very little in their predictions of linear dynamics.…”

“…, and γ 0 , α s and E s 0 are material properties of the coating. We have demonstrated how these characteristic properties for a microbubble contrast agent can be measured through acoustic experiments (Paul et al 2010(Paul et al , 2013Kumar & Sarkar 2015;Xia, Porter & Sarkar 2015;Kumar & Sarkar 2016). For example, for contrast agent Sonazoid, they are γ 0 = 0.019 N m −1 , E s 0 = 0.55 N m −1 , α s = 1.5 and κ s = 1.2 × 10 −8 N s m −1 .…”

“…We have demonstrated how these characteristic properties for a microbubble contrast agent can be measured through acoustic experiments (Paul et al. 2010, 2013; Kumar & Sarkar 2015; Xia, Porter & Sarkar 2015; Kumar & Sarkar 2016). For example, for contrast agent Sonazoid, they are , , and .…”