Modelling the behaviour of microbubble contrast agents for diagnostic ultrasound

Encapsulated microbubble contrast agents that can be injected intravenously constitute one of the most important developments in recent years in ultrasound imaging. These microbubbles oscillate nonlinearly in ultrasound fields and produce nonlinear echoes which can be detected by novel imaging methods. The performance of these novel methods depends strongly on the characteristics of nonlinear scattering by the bubbles. Currently a systematic approach to optimizing them does not exist. This is due in part to the lack of a theoretical model for predicting the acoustic response of microbubble contrast agents. This thesis presents some developments made to address this deficiency.; A theory for the nonlinear motion of a single bubble formed the basis of this study. The model was extended to account for the multiplicity of bubble size and the heterogeneity of the ultrasound field. Experiments were designed and performed to quantitatively test the model. The results generally confirmed the validity of the model, while some quantitative discrepancies led to the hypothesis that the shell plays an important role in nonlinear scattering, which was also confirmed by experiment.