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News & Notes
Acoustic Droplet Vaporization Lab Celebrates A Milestone Year
By Nikolas Charles
Spring 2026
“The evolving research is amazing to watch,” says Oliver Kripfgans, PhD, one of the early developers of the technique. “The people involved in the research and development of ADV are a true blessing.” He delivered a heartfelt speech to the gathering of 60 current and former lab members, alumni and colleagues. Other speakers included key radiology faculty members and mentors including Drs. Paul Carson, Douglas Miller, J. Brian Fowlkes, and Mario Fabiilli.
One of the mutual goals of the research group is to share this technology with other medical schools, health systems and laboratories through its peer reviewed publications and national organizations, both medical and engineering. Another goal is to pursue patents on ADV-based technologies, which is important for clinical translation.
“ADV can be used in many different types of applications,” says Mario Fabiilli, PhD, Associate Professor of Radiology and Biomedical Engineering. For those less familiar with this technique, “ADV is the process by which ultrasound is used to turn perfluorocarbon liquid droplets into gas bubbles.” Once the droplets are injected into the blood-stream, an ultrasound transducer device converts the bioinert liquid droplets into microbubbles, which are the size of red blood cells.
“Because they’re so small, they don’t cause tissue infarcts,” says Dr. Kripfgans. “We intended to create bubbles in situ, that is, directly inside the arteries. These microbubbles are also known as ultrasound contrast agents, which circulate freely through blood stream. These bubbles are called transpulmonary contrast agents because they pass through the capillaries, including the pulmonary bed. Rather than making bubbles out of nothing, which is called cavitation, a fascinating effect to discuss another time, we’re making bubbles out of droplet emulsions,” he says, explaining how bubbles are gas filled objects and droplets are composed of fluid. The ADV process is a phase change, with ultra-sound converting perfluorocarbon droplets into perfluorocarbon bubbles.
“The reason these tiny droplets are vaporized into gas bubbles is because they are triggered by acoustic pulses,” adds Brian Fowlkes, PhD, the director of the ultrasound group, who has investigated diagnostic and therapeutic ultrasound applications for decades. As two of the initial developers of the process, Kripfgans and Fowlkes, with appointments in Radiology and Biomedical Engineering, determined that ADV could have valuable clinical applications.
When Dr. Kripfgans, now Associate Professor, joined U-M as a graduate student in 1996, he began to consider the physics associated with these vaporization events, such as: what causes these bubbles to vaporize? And how rapidly is the vaporization progressing? “He began doing ultra-high-speed photography of vaporization events to learn how the acoustic field in and around these droplets were affecting the vaporization process,” shared Dr. Fowlkes. “One needs to understand that a single ADV event lasts just a few millions of a second only. To put this time scale into perspective, a typical lightning strike lasts for 0.2 to 0.3 seconds, a period during which we could observe 50,000 ADV events,” adds Dr. Kripfgans.
Moving from bench to preclinical research, they discovered that ADV could not only be utilized as a drug delivery system, but it could also be used to locally halt blood flow and occlude a target tissue, potentially allowing clinicians to starve cancer cells. “By tailoring the size of droplets and resulting bubbles, we can control how blood flows into different tissues, even in the brain,” says Dr. Fowlkes. Before ADV, this type of intervention could only be accomplished surgically or by catheterization, now it could be done with this minimally invasive technique or transcutaneously.
Along with Dr. Fabiilli, the ongoing ADV research at U-M is being conducted in the Ultrasonic Cavitation and Calibration Lab by Mitra Aliabouzar, PhD, Research Assistant Professor. “I use ADV as a tool to characterize tissue properties,” says Dr. Aliabouzar, whose research specializes in integrating acoustics, mechanics, and material science to advance the biomedical applications of ultrasound. “ADV is also used to estimate the age of a blood clot by how soft or stiff it is, which can help with identifying the best treatment options.
Detecting changes to the tissue can lead to early detection in diseases like cancer.” In addition to Dr. Kripfgans’ ultra-high-speed camera, which allows us to visualize ADV at these rapid time scales across frequencies relevant to medical ultrasound, the lab also employs a range of highly sensitive hydrophones to capture the acoustic emissions generated by ADV bubbles, providing further insight into bubble dynamics and tissue interactions. These acoustic signals can serve as real-time, noninvasive indicators of bubble activity, enabling monitoring and control of ADV processes for improved diagnostic accuracy and therapeutic precision. As the birthplace of ADV, U-M has played a central role in both developing and expanding the technique, growing its applications from foundational research into diverse diagnostic and therapeutic uses.
While much of Dr. Aliabouzar’s ADV research centers around its potential diagnostic usages, Dr. Fabiilli focuses on its strengths for medical therapy. He loads drugs inside the droplets, which allows him to use ultrasound to control the release of drugs locally. “Another application that is very unique involves loading droplets into implants that then get placed into the body.” This process was recently used for an NIH funded study to develop a treatment for peripheral artery disease by stimulating blood vessel formation. Additional applications include regrowing bone as well as using ADV for treating Type I diabetes.
After more than 25 years of research, the ADV lab scientists continue to work towards real life clinical applications, so that this unique process can be used to benefit the lives of patients.