Duke engineers seek to combine ultrasound 3D imaging and therapy

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Duke University engineers are working to develop ultrasound technology to potentially allow physicians to use high frequency waves both to visualize the heart's interior in three dimensions and then destroy certain heart tissue with heat to correct arrhythmias. The work was detailed in two research papers published in the journal IEEE Transactions on Ultrasonics, Ferroelectronics and Frequency Control and Ultrasonic Imaging last month.

The project is being led by Stephen Smith, the biomedical engineering professor who heads the project at Duke's Pratt School of Engineering. In describing the research Smith said his group's technique may improve on doctors' common methods for destroying -- or "ablating" -- aberrant tissue that makes hearts beat irregularly. That current technique employs radio waves emitted from the end of an electrode probe that touches and excessively heats tissue selected for destruction.

After threading that internal probe into the heart through arteries, physicians must use fluoroscopic imaging to direct the device.

"However, a fluoroscope cannot image soft tissue at all," said Smith. In such cases the heart is no more than a fuzzy background. Under those circumstances, fluoroscopy can provide physicians "only a very gross guidance," he added.

His group's current work builds upon successes in miniaturizing ultrasound 3D imaging probes. Such probes are small enough to insert inside the esophagus to render images of the whole heart.
The team has now built dual-function imaging-plus-ablation ultrasound probes as small as three millimeters -- less than half the size of a dime, Smith said.

"We started using very tiny cables, fitting as many as two hundred into a three millimeter catheter," said Smith. "This advance in cable technology has allowed us to incorporate both 3D imaging and ablation in the same catheter.