Ultrasound imaging needle may transform heart surgery

Scientists have developed a new optical ultrasound needle that can be used to image heart tissue in real-time during keyhole procedures.
The technology has been successfully used for minimally invasive heart surgery in pigs, giving an unprecedented, high-resolution view of soft tissues up to 2.5 centimetres in front of the instrument, inside the body.
Doctors currently rely on external ultrasound probes combined with pre-operative imaging scans to visualise soft tissue and organs during keyhole procedures as the miniature surgical instruments used do not support internal ultrasound imaging.
Researchers at University College London (UCL) and Queen Mary University of London (QMUL) in the UK designed and built the optical ultrasound technology to fit into existing single-use medical devices, such as a needle.

"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 Malcolm Finlay from QMUL.
"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," said Finlay, who co-led the study published in the journal Light: Science & Applications.

"This will reduce the chances of complications occurring during routine but skilled procedures such as ablation procedures in the heart," said Finlay.

"The technology has been designed to be completely compatible with MRI and other current methods, so it could also be used during brain or foetal surgery, or with guiding epidural needles," he said.
The team developed the all-optical ultrasound imaging technology for use in a clinical setting over four years.
The technology uses a miniature optical fibre encased within a customised clinical needle to deliver a brief pulse of light which generates ultrasonic pulses.
Reflections of these ultrasonic pulses from tissue are detected by a sensor on a second optical fibre, giving real- time ultrasound imaging to guide surgery.
One of the key innovations was the development of a black flexible material that included a mesh of carbon nanotubes enclosed within clinical grade silicone precisely applied to an optical fibre, researchers said.

The carbon nanotubes absorb pulsed laser light, and this absorption leads to an ultrasound wave via the photoacoustic effect, they said.
A second innovation was the development of highly sensitive optical fibre sensors based on polymer optical microresonators for detecting the ultrasound waves, the researchers said.