When it comes to obliterating the blood clots that cause deep vein thrombosis, doctors have at least two options: intravascular ultrasound tools or tiny diamond-tipped drills. Unfortunately, both approaches have drawbacks. A new ultrasound "drill" developed by North Carolina State University and the University of North Carolina at Chapel Hill, however, may strike the perfect balance between the two.

Existing ultrasound tools are inserted into a vein, where they emit sonic pulses that disintegrate nearby target clots. What's good about them is the fact that they break clots up into very small particles. This means that little if any blood-thinning medication needs to subsequently be used. That said, their ultrasound pulses are emitted laterally – and not focussed solely on the clot – so damage to the blood vessel itself can also occur.

The diamond-tipped drills are also inserted into a vein, where they physically chew away clots. While they only affect the clot itself, they break it up into large enough pieces that blood thinners are required – and those drugs carry the risk of bleeding.

The new tool attacks clots using low-frequency ultrasound, but the pulses are focussed forward into the clot. As a result, there's no collateral damage to the vein, yet the clot is still thoroughly disintegrated. The device is additionally able to inject microbubbles at the clot site, which make the ultrasound more effective.

In lab tests, a prototype was used in a synthetic blood vessel filled with cow's blood. "We found that we could dissolve 90 percent of a clot in 3.5 to 4 hours without using any blood thinners at all," says North Carolina State PhD student Jinwook Kim, lead author of a paper on the research. "That's compared to 10 hours for the combination of conventional ultrasound tools and blood thinners."

The research team is now looking towards animal trials, and is seeking industry partners to help develop the technology.