Effects of liquid compressibility on the dynamics of ultrasound contrast agent microbubbles

Ultrasound contrast agents (UCA) have been widely used in ultrasonic medical applications. The dynamics of UCA should be simulated accurately to maximize the application effects. The acoustic radiation of UCA oscillations is affected by the liquid compressibility which has to be considered. This paper deduces a simple equation based on Keller-Miksis equation to describe the dynamics of UCA with a polymer shell, taking consideration of compressibility of the liquid. The volume of UCA shell is constant. The shell is described by the Kelvin-Voigt viscoelasticity model.The extended compressible model is verified by comparing with experimental data and Hoff model in predicting the variations of bubble radius with time, resonance frequency, damping constants and acoustical scattering cross section of the UCA microbubbles. The physical explanations of the differences between the extended compressible model and Hoff model in predicting resonance frequency and acoustical scattering cross section are listed. The liquid compressibility correction in UCA model can be better used to predict the bubble dynamics at large radius with high excitation frequency, and it will give us some valuable references in ultrasonic medical applications. (paper)