Bubble evolution in acoustic droplet vaporization at physiological temperature via ultra-high speed imaging

Acoustic droplet vaporization in a rigid tube at body temperature was investigated experimentally using an ultra-high speed camera. This study was motivated by gas embolotherapy, a developmental cancer treatment in which gas microbubbles that are selectively formed by acoustically vaporizing liquid droplets in vivo are used to occlude tumor blood flow. The evolution of microbubbles formed by acoustic droplet vaporization was analyzed and a four-stage empirical curve was fit to the growth. Viscous resistance from the tube was shown to dampen oscillations of the microbubbles even though the bubble diameter was smaller than the tube diameter. The results suggest that, for some parameter values, vaporization may still be occurring when the bubble expansion starts and indicate the importance of this in modeling the growth of bubbles formed by acoustic droplet vaporization.