Ultrasound needle enables clear imaging during heart procedures

The first optical ultrasound needle enables real-time imaging of heart tissue during minimally invasive procedures, according to researchers in the United Kingdom.

The device was developed by scientists at University College London (UCL) and Queen Mary University of London, according to a study published in Light: Science and Applications, and has been successfully used for keyhole surgery in swine models. The technology is “revolutionary,” a UCL news release stated, because clinicians have had to rely for decades on x-ray fluoroscopy and external ultrasound probes to visualize soft tissue during surgery.

“The optical ultrasound needle is perfect for procedures where there is a small tissue target that is hard to see during keyhole surgery using current methods, and missing it could have disastrous consequences,” co-lead author and doctor Malcolm C. Finlay said in the release.

Over four years, Finlay and his team developed the needle device, which is composed of inexpensive optical fibres, the authors explained in the study. The needle’s sensitivity was key, since the goal was to image centimeter-scale depths of tissues while it moves. The technology had to produce high-resolution images using needle tips under one millimeter in size, Finlay et al. wrote, and needed to fit into existing clinical workflow.

Optical fiber encased in a clinical needle delivers a quick pulse of light during surgery, which generates ultrasonic pulses, according to the research. Reflections of the pulses from tissue are then detected by a sensor on another optical fiber, producing real-time ultrasound images clinicians can follow.

“The whole process happens extremely quickly, giving an unprecedented real-time view of soft tissue,” co-lead author Richard J. Colchester said in the release. “It provides doctors with a live image with a resolution of 64 microns, which is the equivalent of only nine red blood cells, and its fantastic sensitivity allows us to readily differentiate soft tissues.”

According to the study, the researchers tested the needle within the beating heart of a pig, providing what they called “real-time views” of cardiac tissue. With the new technology, Finlay and colleagues were able to view clear images of anatomical structures required for a safe transseptal crossing, including right and left atrial walls, the right atrial appendage and the limbus fossae ovalis.

High-frequency ultrasound imaging provides “exquisite” visualizations of tissue to guide keyhole procedures, the authors wrote, but is underutilized in clinical practice since no device like their needle had been developed up to this point. Finlay et al. did, however, design the technology to be compatible with MRI and other popular imaging methods so it can be applied to other surgeries, like brain or fetal procedures.

“We now have real-time imaging that allows us to differentiate between tissues at a remarkable depth, helping to guide the highest risk moments of these procedures,” Finlay said. “This will reduce the chances of complications occurring during routine but skilled procedures such as ablation procedures in the heart.”