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 pressuredependent resonances ( f s ). It was shown that when excited by the ( f s ), the UCA can undergo a saddlenode 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.

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Endovascular medical devices such as catheters are composed of multiple thermal plastic components joined by buttwelding. High quality joining of components is required to ensure patient safety. The current practice for assuring quality is limited to process validation and destructive testing. An ultrasonic system for endovascular weld inspection was developed to detect faults (porosity and contamination) post welding in polyamide (Pebax-72D). Results from angled ultrasonic measurements were compared to micro-CT and found to correlate well with weld quality as a potential nondestructive index for 100% in-line verification of the joining process.