The effect of microbubble concentration on thresholds for tissue damage produced by single bursts of high intensity ultrasound during continuous Optison® infusion

The presence of ultrasound contrast agent (stabilized microbubbles) during high intensity focused ultrasound insonation can reduce both the exposure intensity and duration required for producing macroscopic tissue damage. In this paper, we evaluate the enhancement produced by Optison® infusion at concentrations of 0, 0.1, 0.3, 1, 3, and 10 μL/kg/min. Acute canine kidneys were surgically externalized and insonified with single ultrasound exposures. The probability of tissue damage production was determined with respect to exposure intensity and duration for each concentration. As microbubble concentration increased from 0 to 10 μL/kg/min, the requisite intensity and the requisite duration both gradually decreased. The results indicate that microbubble introduction up to 10 μL/kg/min is effective for aiding ultrasound therapy.