Wideband Excitation of Microbubbles with Chirps to Maximize the Sonoporation Efficiency and Contrast in Ultrasound Imaging

TL;DR

This study investigates how wideband chirp excitation improves microbubble resonance and sonoporation efficiency in ultrasound therapy, showing that low-intensity, long-duration excitation enhances stable oscillations and energy transfer.

Contribution

It demonstrates the benefits of wideband chirp excitation for microbubbles in therapeutic ultrasound, emphasizing stable oscillations over inertial cavitation for improved sonoporation.

Findings

Wideband excitation maximizes microbubble energy emission.

Long duration, low intensity excitation promotes stable oscillations.

Stable oscillations enhance sonoporation efficiency.

Abstract

The importance of the excitation bandwidth is well known in diagnostic ultrasound imaging. However, the effect of excitation bandwidth in therapeutic applications of microbubbles has been mostly overlooked. A majority of contrast agent production techniques generate polydisperse microbubble populations, so a wide range of resonance frequencies exist. Therefore, wideband excitation is necessary to fully utilize microbubble resonance behavior and maximize the reradiated energy from a microbubble population, both for imaging and therapy. Oscillations of sixty SonoVue microbubbles in proximity of a rigid boundary were captured on a high speed camera at 3 Mfps, excited with a peak negative pressure of 50 kPa at 1 MHz. Measurements were analyzed according to their peak radiated pressure, radial oscillations, root mean squared pressure, and shear stress generated by microbubbles. Results showed that long duration and wideband excitation at low intensity levels was preferable for sonoporation, where microbubbles can be driven in a stable oscillation state without experiencing inertial cavitation or destruction.