Jain, Pankaj2020-09-252020-09-252006https://udspace.udel.edu/handle/19716/27746Ultrasound contrast agents are micron size bubbles used for medical purposes such as diagnostic ultrasound imaging and targeted drug delivery. These bubbles are encapsulated with a shell and have a sparingly soluble gas inside to prevent them from premature dissolution. When these bubbles are excited by the ultrasound they scatter and absorb energy from the sound field, thus leading to the attenuation of the ultrasound signal. In this thesis, we have developed a viscous and a viscoelastic model for the shell. Attenuation measured in vitro is compared with model predictions to obtain the characteristic model parameters (surface tension, shell elasticity, dilatational viscosity) for commercially available contrast agents. The viscous model predicts unusually high values of surface tension which motivated the viscoelastic model. We have also used both models to predict the scattered response of microbubbles. ☐ Experimentally measured attenuation is also used to study the growth and destruction of contrast microbubble Definity® (Bristol Meyers Squibb, N. Billerica, MA). Critical pressure amplitudes of ultrasound excitation leading to destruction of contrast microbubbles have been identified for different Pulse Repetition Frequencies (PRFs). ☐ We have developed a model for the growth and dissolution of encapsulated microbubbles taking into account the hindered permeability and elasticity of the encapsulation. We investigated the effects of parameters such as mole fraction of the osmotic agent (inside gas), surface tension, shell permeability, and air saturation level in bulk.Ultrasound contrast mediaMicrobubblesViscoelasticityViscosityThesis85811732