The effects of fluid compressibility on multibubble cavitation for high‐intensity focused ultrasound.

In this talk the effects of liquid compressibility and viscosity on cavitation occurring during high‐intensity focused ultrasound treatments are discussed. Using techniques from dynamical systems analysis, the criterion for inertial cavitation is formally generalized for multi‐bubble models. It is shown that the threshold for inertial cavitation remains independent of the number of bubbles present. It is conjectured that this is because the re‐radiated pressure field from any one bubble only has a significant influence on the oscillations of the surrounding bubbles if it collapses inertially. For interacting bubbles the effects of compressibility are analyzed through the inclusion of the appropriate time delays in the bubble interactions. This may result in instability, but it is shown that for values of viscosity relevant to tissue, the system is stable. Instabilities may develop in the full system limiting the ability of a bubble to undergo repetitive bounded oscillations. There are four main mechanisms...