Evaluation Of The Effects Of Secondary Radiation Force On Aggregation Of Microbubbles

Recently with the rapid development of microbubble-preparation and ultrasonic diagnostic technology, ultrasound contrast agents have shown promising prospects in ultrasonic molecular imaging and targeting drug/gene therapy. An ultrasonic wave impacts two different types of acoustic radiation forces on the microbubbles. The primary radiation force is generated from the gradient of the time averaged acoustic pressure around the microbubble; while the secondary radiation force is induced between two vibrating microbubbles, causing them to attract or repel each other. The study of secondary radiation force is essential for further promoting the clinical application of ultrasonic molecular imaging and targeting drug delivery.Based on the modified Herring equation and Newton equation of motions, this thesis established a theoretical model of two interacting encapsulated bubbles to describe the dynamics and kinematics of group behavior. In the numerical simulations, this study discussed the attraction and repulsion condition for microbubbles, analyzed the physical mechanism of microbubble aggregate in ultrasonic molecular imaging, and offered suggestions on the optimization of ultrasonic sound pressure and frequency and contrast agent concentration to reduce microbubble aggregations.