RALEIGH, N.C. — Blood flow in and out of the brain is incredibly important. Lack of blood reaching the brain can lead to the death of brain cells, while a blockage impeding blood from draining out of the brain can cause a hemorrhage. Now, however, scientists at North Carolina State University have created a tornado-like tool that is capable of breaking down blood clots in the brain.
What is this new technology? Researchers say the approach makes use of vortex ultrasound, or a type of ultrasonic “tornado” that works faster than existing techniques currently available to eliminate clots formed in an in vitro model of cerebral venous sinus thrombosis (CVST).
“Our previous work looked at various techniques that use ultrasound to eliminate blood clots using what are essentially forward-facing waves,” says Xiaoning Jiang, co-corresponding study author, in a university release. “Our new work uses vortex ultrasound, where the ultrasound waves have a helical wavefront.”
“In other words, the ultrasound is swirling as it moves forward,” explains Jiang, who is the Dean F. Duncan Professor of Mechanical and Aerospace Engineering at NC State. “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,” adds Chengzhi Shi, co-corresponding author of the work and an assistant professor of mechanical engineering at Georgia Tech. “This increases the risk of a hemorrhage 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.”
Blood clot cases are going up
CVST occurs when a blood clot forms within the veins responsible for draining blood out of the brain. Incidence rates of CVST were between two and three per 100,000 people in the United States in 2018 and 2019. Even more concerning, the incidence rate appears to be increasing since then.
“Another reason our work here is important is that current treatments for CVST fail in 20-40% of cases,” Prof. Jiang notes.
The tool consists of one transducer specially designed to create the swirling, vortex effect. The device is also small enough to fit inside a catheter, which doctors can feed through the circulatory system to the location of the blood clot. To facilitate their proof-of-concept in vitro testing, researchers used cow blood placed within a 3D-printed model of the cerebral venous sinus.
“Based on available data, pharmaceutical interventions to dissolve CVST blood clots take at least 15 hours, and average around 29 hours,” Prof. Shi reports. “During in vitro testing, we were able to dissolve an acute blood clot in well under half an hour.”
The new tool may cause fewer surgical injuries
There is always a risk of harm during any catheterization or surgical intervention. For example, damaging the blood vessel itself. In an attempt to address this concern, study authors conducted a series of experiments applying vortex ultrasound to animal blood vein samples. Those tests did not produce any evidence of damage inflicted to the walls of the blood vessels. Further tests were conducted to gauge if the vortex ultrasound caused significant damage to red blood cells, but no substantial damage was noted.
“The next step is for us to perform tests using an animal model to better establish the viability of this technique for CVST treatment,” Prof. Jiang says. “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,” Prof. Shi concludes.
The study is published in the journal Research.