Influence of the pressure-dependent resonance frequency on the bifurcation structure and backscattered pressure of ultrasound contrast agents: a numerical investigation

The bifurcation structure of the oscillations of ultrasound contrast agents (UCAs) was studied as a function of the driving pressure for excitation frequencies that were determined using the UCAs pressure-dependent resonances ( f s ) . It was shown that when excited by the ( f s ) , the UCA can undergo a saddle-node bifurcation (SNB) to higher amplitude oscillations. The driving pressure at which the SNB occurs is controllable and depends on the ( f s ) magnitude. Utilizing the appropriate ( f s ) , the scattering cross section of the UCAs can significantly be enhanced (e.g., ∼ ninefold) while at the same time avoiding potential UCA destruction (by limiting the radial expansion ratio < 2). This offers significant advantages for optimizing UCA-mediated imaging and therapeutic ultrasound applications.