On the impact of vessel size on the threshold of bubble collapse

Abstract

Most of the studies investigating the physical properties of ultrasound contrast agents have addressed situations in which the microbubbles are contained in vessels much larger than the bubble size. Since contrast agents are normally injected into blood vessels, the investigation of their behavior in a confined environment may reveal useful information for the optimization of diagnostic and therapeutic applications of ultrasound. A series of experiments involving an ultrasound contrast agent in different sized silica and polyester tubes ranging from 50 to 400 microns in internal radius is presented. It is shown that the threshold for bubble collapse, as recorded by broadband acoustic emission, is not only dependent on the applied pressure amplitude but also on the tube size with an increase for smaller vessels. These data are interpreted and rationalized on the basis of a simple physical model. These findings may have implications for the evaluation of the risk of inertial cavitation in blood vessels. [Work supported by NIH RO1-EB003268 and by the Brigham Radiology Research and Education grant.]