Use of ultrasound contrast agents can significantly improve ultrasound blood flow images. These are micron-size gas bubbles that are intravenously injected into patients’ body at the time of ultrasound imaging. The bubbles are encapsulated by a thin layer ( ~ 4-10nm) of protein, lipids and other surface active materials, to prevent their premature dissolution in the blood. Strong ultrasound pulses can destroy these bubbles by rupturing the encapsulation. Destruction of microbubble agents can be used in real time blood flow velocity measurement, stimulating arteriogenesis (generation of new arteries) or targeted drug delivery. The encapsulation critically affects the performance of these agents in all applications. We have developed an interface model of the encapsulation that has an intrinsic surface rheology with surface viscosity and elasticity. Our hypothesis is that a model for contrast agent, if it retains the essential physics, will offer applicability over a wide range of acoustic pressure amplitudes and frequencies. Specifically, we propose a validation test for our model by examining its ability to predict the nonlinear response. In this talk, I will describe our approach that includes determination of rheological properties using one set of in vitro experiment, and then model validation using another set. Data on several contrast agents such as Sonazoid (Amersham Health, Oslo, Norway), Optison (GE Health Care, Princeton, NJ), Definity (Bristol Myers Squibb, N. Billerica, MA) will be presented. I will also report our findings on ultrasound mediated destruction of Definity microbubbles ¾ critical parameters, and different mechanisms of destruction. In the end, I will briefly discuss our research on computational multiphase flow. I will present our recent findings on finite inertia effects on rheology of emulsion, resonance in drop shapes, effects of shear waves on drop dynamics and hydrodynamics mediated interaction between drops