Researchers in London have published details of a revolutionary new cardiology needle capable of imaging the heart’s soft tissues from within. The team from University College London (UCL) and Queen Mary University of London (QMUL) used the new all-optical ultrasound imaging system for heart surgery in pigs, successfully capturing high-resolution images up to 2.5cm away from the needle tip.
An all-optical ultrasound device may sound like an oxymoron, but the imaging needle relies on an embedded miniature optical fiber that transmits brief pulses of light, which in turn generate ultrasonic pulses. These ultrasonic pulses propagate away from the needle, reflecting off soft tissues before being detected by a second optical fiber in the needle housing.
For the first time live imaging can now be taken directly from inside the heart during keyhole surgery, which has the potential to offer vast improvements over current practice, where surgeons rely on preoperative imaging combined with external ultrasound probes.
“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,” said Dr Malcolm Finlay, study co-lead and consultant cardiologist at QMUL and Barts Heart Centre.
The needle system can emit ultrasound thanks to the development of a novel composite material consisting of a mesh of carbon nanotubes encased in silicone and located on the tip of the optical fiber. The pulsed light from the fiber is absorbed by the carbon nanotubes and produces an ultrasound wave due to the photoacoustic effect. A second innovation underpins the detection of the reflected ultrasound waves at such a small scale, which is the invention of highly sensitive optical fibers incorporating polymer optical microresonators.
The incredibly high speed of the ultrasound emission and detection process results in unprecedented temporal and spatial resolution of the images. The current system can provide live imaging with a resolution as fine as 64 microns, which is about the width of nine red blood cells. The movement of the heart walls and valves can also be tracked in real time.
Outside of cardiology, the imaging system has many potential uses in a variety of minimally invasive procedures, and it even opens-up the possibility of futuristic applications such as in-womb surgery.
The team of researchers behind the technology are now planning towards translating the system for clinical use in patients.
Open access study in journal Light: Science & Applications: Through-needle all-optical ultrasound imaging in vivo: a preclinical swine study…
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