Real-time, three-dimensional images from inside veins and arteries should soon be available to surgeons conducting heart surgery thanks to a camera 1.5mm across but with the capacity to produce 60 frames a second with a view of the inside of a vessel in multiple directions.
It's not quite Fantastic Voyage, where a miniaturized submarine a micrometer across travels through the blood system to break up a clot, but Professor F. Levent Degertekin has put a 20MHz ultrasonic transducer on a chip small enough to fit on the end of a wire that can follow the bends of the body to get from a limb to the heart.
“Our device will allow doctors to see the whole volume that is in front of them within a blood vessel,” says Degertekin, of the Georgia Institute of Technology. “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.”
“If you’re a doctor, you want to see what is going on inside the arteries and inside the heart, but most of the devices being used for this today provide only cross-sectional images,” Degertekin explains. “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.”
Degertekin, whose work is published in IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, squeezed 56 ultrasonic transmitters and 48 receivers onto the tiny chip, along with a hole in the center for the guide wire. If that isn't enough he also processes some of the data on the chip in order to reduce the size of the cables required to transmit information back to the surgeons. “You want the most compact and flexible catheter possible,” Degertekin says.
This all operates on an average 20mW, shutting down when not required, which prevents overheating. This is more important than it may sound – some prototypes would have caused the patient's blood to boil literally, probably setting off a figurative blood boiling in the surgical team. The body absorbs high frequency ultrasound too much to allow a 20MHz signal from the outside. Lower frequency sensors (usually 3-5MHz) don't offer the resolution required for surgeons to target blood clots.
The device is yet to be tested in living animals, let alone humans, but has operated successfully inside a removed chicken heart. Degertekin believes it will replace the two technicians currently in the operating theater to translate low resolution images to instructions to the surgeon, cutting costs at the same time as the invasiveness of the surgery will come down.
Just like in Numb3rs Degertekin identified the need through conversations with his brother, a cardiologist. “I get lots of ideas from talking with him,” he told Wired Magazine. “He gave us the idea of miniaturizing this even further so we can put this technology on a guide wire.” However, the idea may prove useful for other areas of the body, with Degertekin contemplating fitting it to scalpel blades to give surgeons a better idea of how deep they should cut.