1B-5 Surface Modes of Ultrasound Contrast Agent Microbubbles

We study non-spherical oscillations (surface modes) of the coated microbubbles used in ultrasound contrast agents. We show that an acoustic pressure of 100 kPa, at a frequency of 1.7 MHz, is sufficient to excite surface modes for radii between 2 and 4 mum. Surface modes develop as a parametric instability. We derive their evolution equation accounting for the effect of the shell viscoelasticity. We identify a critical radius (1 to 3 mum, depending on the mode number) below which no surface mode can occur