Light-scattering measurements of cavitation from ultrasound contrast agent bubbles

Abstract

Ultrasound contrast agents are typically micron-sized gas bodies with stabilizing shell coatings. The shell prevents the gas bubble from dissolving. The shell also changes a bubble’s scattering properties and affects a bubble’s destruction. Optimization of the shell can be beneficial for diagnostic imaging and therapeutic ultrasound applications. Thus, understanding agent response to pulsed ultrasound is important. However, because the agents are so small, their response to pulsed ultrasound is difficult to measure. Until recently, the only tool available for measuring contrast agent dynamics was a very expensive high-speed camera. We have been investigating the use of light-scattering to measure aspects of cavitation from contrast agents in which a small HeNe laser beam scatters off a bubble and is focused onto a photomultiplier tube detector. Previous experiments have involved clusters of agents, where collective bubble oscillations and destruction were observed. Our current apparatus is designed to observe single-bubble oscillations from a diagnostic ultrasound system. The advantages for using light-scattering include small cost and the ability to monitor bubble oscillations for extended times. The technique will be described, and representative data samples will be shown.