Tiny 3D ultrasound probe guides catheter procedures

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An ultrasound probe, small enough to ride along at the tip of a catheter, can provide physicians with clearer real-time images of soft tissue without the risks associated with conventional x-ray catheter guidance, according to study results published in the September issue of IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

Biomedical engineers at Duke University in Durham, N.C., designed and fabricated the probe, which they said can provide detailed, 3D, blended images from 108 miniature transducers.

Catheter-based procedures involve snaking instruments through blood vessels, usually with the guidance of x-ray images. Often, a contrast agent is injected into the bloodstream to highlight the vessel.

Stephen W. Smith, PhD, director of the Duke University Ultrasound Transducer Group and senior member of the research team, said that “there are many catheter-based interventional procedures where 3D ultrasound guidance could be used, including heart valve replacements and placement of coils in the brain to prevent stroke. Wherever a catheter can go, the probe can go.”

 “The 3D ultrasound guidance does not use x-ray radiation or contrast agents, and the images are real-time and continuous,” said research engineer Edward Light, first author of the paper and designer of the new probe. He added that while the images obtained this way are of good quality, some patients experience adverse reactions to the contrast agent. Additionally, images gained this way are fleeting.

In a series of proof-of-principle experiments in a water tank using simulated vessels, the engineers used the new ultrasound probe to guide the placement of a filter within a vessel and the placement of a synthetic "patch" for aortic aneurysms. The scientists said they plan to begin tests of the new system in animals within the year.

In the first experiment, the new probe successfully guided the placement of a filter in a simulated vena cava. The second experiment involved the placement of abdominal aorta aneurysm stent grafts.

"I believe we have shown that 3D ultrasound clearly works in a wide variety of interventional procedures," Smith said. "We envision a time in the not-too-distant future when this technology becomes standard equipment in various catheter kits."

The National Institutes of Health provides funding for the research conducted in Smith’s lab.