3D sonar fits in blood vessel for medical imaging

On-chip signal processing allows the data to be sent down 13 cables, which would form a catheter.

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“You want the most compact and flexible catheter possible. We could not do that without integrating the electronics and the imaging array on the same chip,” said Georgia professor Degertekin.

The prototype sends images at 60frame/s from a dual-ring of 56 transmit elements and 48 receive elements. Each element is a 20MHz capacitive micro-machined ultrasonic transducer (CMUT), and the front-end electronics is CMOS.

When assembled, the doughnut-shaped array is 1.5mm in diameter with a 430µm centre hole to accommodate a guide wire.

Power-saving circuitry in the array shuts down sensors when they are not needed, allowing the device to operate on 20mW.

In medical speak, it provides three-dimensional intra-vascular ultrasound (IVUS) and intra-cardiac echography (ICE) images.

“Our device will allow doctors to see the whole volume that is in front of them within a blood vessel. This will give cardiologists the equivalent of a flashlight so they can see blockages ahead of them in occluded arteries. It has the potential for reducing the amount of surgery that must be done to clear these vessels,” said Degertekin. “Most of the devices being used for this today provide only cross-sectional images. If you have an artery that is totally blocked, for example, you need a system that tells you what’s in front of you. You need to see the front, back and sidewalls altogether. That kind of information is basically not available at this time.”

Are the images good enough so far? Degertekin and his collaborators obtained what they believe are clinically-useful images with only 13 cables,” said Georgia.

Based on the prototype, animal trials are expected.

For the future, Degertekin hopes to develop a version of the device that could guide interventions in the heart under magnetic resonance imaging (MRI). Other plans include reducing the size of the device to place it on a 400µm diameter guide wire.

Along with a multi-disciplinary team from Georgia Tech, the team included Professor Mustafa Karaman of Istanbul Technical University.

The work is published as ‘Single-chip CMUT-on-CMOS front-end system for real-time volumetric IVUS and ICE Imaging‘ in the IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.