Acoustic Characterization of Shell and Size Engineered Microbubbles

Acoustically activated microbubbles are being used for molecular imaging, targeted drug delivery, and opening the impermeable blood-brain-barrier. However, our limited understanding of microbubble oscillation dynamics can hinder the ability to leverage their full potential in ultrasound applications. In the response to ultrasound, microbubble oscillations can be highly nonlinear, and the presence of a shell adds to the complexity of their oscillatory behavior, but previous models predicting microbubble behavior were based on linear assumptions. The focus of this project is to characterize the physical shell properties of microbubbles using attenuation measurements. The behavior of these microbubbles was observed to be linear at pressures between 4.6-10 kPa and they started to oscillate non-linearly at higher pressures. The estimated shell parameters suggest a higher shell elasticity at lower pressures and higher shell viscosity at higher pressure. Understanding microbubble behavior would help researchers to optimize the use of microbubbles and increase their therapeutic potential.