| This work presents two studies of dynamic microbubble behavior. The first study is experimentation performed to examine the controlled destruction of ultrasound contrast agents and the other study deals with the development of a computational model to simulate the dynamics of a single, spherical microbubble.; In the experimental study, a dual-frequency imaging method is used to examine the effect of lower transmitted frequencies on contrast agent destruction. In this imaging method, backscatter is measured at various liquid flow rates using a high frequency (2.25 MHz) imaging transducer while a low frequency transducer (50 and 100 kHz) is used to destroy the contrast microbubbles. The intensity of the backscatter is an indicator of ultrasound contrast agent destruction since it is proportional to the amount of ultrasound contrast agent present. The results show that the acoustic signal returned from the contrast agents is suppressed at transmitted pressure amplitudes between 17 kPa to 50 kPa when using the low frequency transducer, indicating contrast agent destruction. The controlled destruction of ultrasound contrast agents is significant in medical applications such as drug delivery and blood flow measurements.; The computational model presented examines the behavior of single microbubble against a solid boundary using the immersed boundary method. The Navier-Stokes equations, which describe the flow in the fluid surrounding the bubble, are solved using a semi-implicit pressure correction method and the diffusion equation is solved using a standard control-volume scheme. This model serves as an aid in predicting the lifetime of a bubble, with a specified initial radius, resting against a wall, and provides a means of determining the behavior of bubbles located on internal surfaces or container walls. |
