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New Ultrasound Device May Help Detect Risk for Heart Attack, Stroke

Intravascular transducer identifies vulnerable plaque

Researchers at North Carolina State University and the University of North Carolina at Chapel Hill have developed an ultrasound device that could help identify arterial plaque that is at high risk of breaking off and causing a heart attack or stroke.

At issue is the plaque that builds up in arteries as people age. Some types of plaque are deemed “vulnerable,” meaning that they are more likely to detach from the artery wall and cause a heart attack or stroke.

“Existing state-of-the-art technologies are capable of determining if plaque is present in the arteries but can’t tell whether it’s vulnerable. And that makes it difficult to assess a patient’s risk,” said co-author Dr. Paul Dayton. “Our goal was to develop something that could effectively identify which plaques are vulnerable.”

Two ultrasound techniques currently help identify vulnerable plaques, but both techniques depend on the use of contrast agents called “microbubbles.”

The first technique is to identify vasa vasorum in arteries. These are clusters of small blood vessels that often infiltrate arterial plaque. These blood vessels are considered to be indicators that a plaque is vulnerable. When microbubbles are injected into an artery, they follow the flow of the blood. If vasa vasorum are present, the microbubbles will flow through these blood vessels as well, effectively highlighting them on ultrasound images.

The second technique is molecular imaging, which relies on the use of “targeted” microbubbles. These microbubbles attach themselves to specific molecules that are more likely to be found in vulnerable plaques, making the plaques stand out on ultrasound images.

“The problem is that existing intravascular ultrasound technology does not do a very good job in detecting contrast agents,” said co-author Dr. Xiao-ning Jiang.

“So we’ve developed a dual-frequency intravascular ultrasound transducer, which transmits and receives acoustic signals,” Jiang said. “Operating on two frequencies allows us to do everything the existing intravascular ultrasound devices can do, but also makes it much easier for us to detect the contrast agents — or microbubbles — used for molecular imaging and vasa vasorum detection.”

The prototype device has performed well in laboratory testing, but the researchers say they are continuing to improve the technology. They hope to launch preclinical studies in the near future.

The research was supported by the National Institutes of Health.

Source: North Carolina State University; April 24, 2013.

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