Inside information for endoscopy

A tiny, sensitive, ultrasound probe which gives three-dimensional images from inside the body during endoscopic surgery is ready to begin human trials.



Researchers at Duke’s Pratt School of Engineering in the US have used the device to image the beating hearts of dogs. The engineers said their demonstration showed that the probes could give surgeons a better view during human endoscopic surgeries, in which operations are performed through tiny “keyhole” incisions.



If the probes prove beneficial in human testing, the advance might lead to more precise and safer endoscopic surgeries, said the Duke engineers.



“Surgeons now use optical endoscopes or two-dimensional ultrasound when conducting minimally invasive surgery,” said lead engineer Stephen Smith, a professor of biomedical engineering at the Pratt School.



“With our scanner, doctors could see the target lesion or a portion of an organ in a real-time three-dimensional scan,” Smith said. “They would have the option of viewing the tissue in three perpendicular cross-sectional slices simultaneously or in the same way a camera would see it, except that a camera can’t see through blood and tissue.”



The technology has yet to be tested in human patients, but its success in dogs makes it ready for clinical trials, according to the researchers.



Duke developed the first 3D ultrasound scanner in 1987 for imaging the heart from outside the body. As technology enabled ever-smaller ultrasound arrays, the researchers engineered probes that could fit inside catheters threaded through blood vessels to image the vasculature and heart from the inside out.



The current advance relies on 500 tiny cables and sensors packed into a tube 12 millimetres in diameter, the size required to fit into surgical instruments, called trocars, that surgeons use to allow easy exchange of laparoscopic tools. By comparison, most two-dimensional ultrasound probes use just 64 cables.



Each cable carries electrical signals from the scanner to the sensors at the tip of the tube, which in turn send pulses of acoustic waves into the surrounding tissue, Smith said. The sensors then pick up the returning echoes and relay them back to the scanner where they produce an image of the moving tissue or organ. The scanner uses parallel processing to listen to echoes of each pulse in 16 directions at once.



The laparoscopic ultrasound probes have so far been applied only to heart imaging, in which they may be particularly useful for monitoring heart function during minimally invasive cardiac surgery, Smith said. Current methods often monitor the heart with a 2D ultrasound endoscope probe down the throat, a method that requires general anaesthesia.



Similar 3D ultrasound devices also hold promise for minimally invasive abdominal and brain surgery applications, Smith said.