High-speed photography during ultrasound illustrates potential therapeutic applications of microbubbles.

Ultrasound contrast agents consist of microscopically small encapsulated bubbles that oscillate upon insonification. To enhance diagnostic ultrasound imaging techniques and to explore therapeutic applications, these medical microbubbles have been studied with the aid of high-speed photography. We filmed medical microbubbles at higher frame rates than the ultrasonic frequency transmitted. Microbubbles with thin lipid shells have been observed to act as microsyringes during one single ultrasonic cycle. This jetting phenomenon presumably causes sonoporation. Furthermore, we observed that the gas content can be forced out of albumin-encapsulated microbubbles. These free bubbles have been observed to jet, too. It is concluded that microbubbles might act as a vehicle to carry a drug in gas phase to a region of interest, where it has to be released by diagnostic ultrasound. This opens up a whole new area of potential applications of diagnostic ultrasound related to targeted imaging and therapeutic delivery of drugs such as nitric oxide.