Researchers have developed a novel instrument and approach for breaking down blood clots in the brain that use “vortex ultrasound” a form of ultrasonic tornado. The novel method removed clots more quickly than previous procedures in an in vitro model of cerebral venous sinus thrombosis (CVST). The study’s findings were published in the journal Research.
“Our previous work looked at various techniques that use ultrasound to eliminate blood clots using what are essentially forward-facing waves,” said Xiaoning Jiang, co-corresponding author of a publication on the topic. “Our new technique employs vortex ultrasound, which produces ultrasound waves with a helical waveform.
“In other words, the ultrasound is swirling as it moves forward,” said Jiang, who is the Dean F. Duncan Professor of Mechanical and Aerospace Engineering at North Carolina State University. “Based on our in vitro testing, this approach eliminates blood clots more quickly than existing techniques, largely because of the shear stress induced by the vortex wave.”
“The fact that our new technique works quickly is important, because CVST clots increase pressure on blood vessels in the brain,” said Chengzhi Shi, co-corresponding author of the work and an assistant professor of mechanical engineering at Georgia Tech. “This increases the risk of a haemorrhage in the brain, which can be catastrophic for patients.
“Existing techniques rely in large part on interventions that dissolve the blood clot. But this is a time-consuming process. Our approach has the potential to address these clots more quickly, reducing risk for patients.”
CVST happens when a blood clot develops in the veins that drain blood from the brain. CVST incidence rates in the United States were between 2 and 3 per 100,000 in 2018 and 2019, and the rate appeared to be growing.
“Another reason our work here is important is that current treatments for CVST fail in 20-40% of cases,” Jiang said. The new device is made up of a single transducer that is particularly engineered to create the whirling, vortex effect. The transducer is tiny enough to fit inside a catheter, which is subsequently sent through the circulatory system to the location of the blood clot. The researchers employed cow blood in a 3D-printed replica of the cerebral venous sinus for proof-of-concept in vitro testing.
“Based on available data, pharmaceutical interventions to dissolve CVST blood clots take at least 15 hours, and average around 29 hours,” Shi said. “During in vitro testing, we were able to dissolve an acute blood clot in well under half an hour.”
There is a danger of injury with any catheterization or surgical intervention, such as injuring the blood artery itself. To address this issue, the researchers conducted studies on animal blood vein samples using vortex ultrasound. These examinations revealed no damage to the blood vessel walls.
The researchers also tested to see if the vortex ultrasound produced any major harm to red blood cells. They discovered that there was no significant damage to red blood cells.
“The next step is for us to perform tests using an animal model to better establish the viability of this technique for CVST treatment,” Jiang said. “If those tests are successful, we hope to pursue clinical trials.”
“And if the vortex ultrasound ever becomes a clinical application, it would likely be comparable in cost to other interventions used to treat CVST,” said Shi.
