Modelling oscillations of a microbubble in an elastic vessel

Encapsulated microbubbles have been extensively investigated as contrast agents for diagnostic ultrasound imaging and more recently for therapeutic applications such as drug delivery. However, theoretical models for microbubble dynamics exist either for encapsulated bubbles in an infinite volume of liquid, or for unencapsulated bubbles in a confined volume. In the present study, a finite‐element method is applied to quantify the effects of both encapsulation and confinement in a blood vessel upon a microbubble’s response to ultrasound. The effect of encapsulation is examined for polymeric and surfactant coatings. Elastic deformations of the vessel wall are described using a lumped‐parameter model, treating the wall as a thin membrane. It will be shown that even at low acoustic pressures (10 kPa), the bubble oscillations can be significantly modified as a result of confinement. In particular, the frequency spectrum of the oscillations of a confined bubble is characterized by two modes. For relatively soft ...