Medical camera makes ‘light work’ of seeing through the body

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The camera being developed will help clinicians to locate light sources – such as the tips of endoscopes – that have been inserted into the human body.

Members of the Proteus team, led by Proteus Co-Investigator Prof. Robert R. Thomson and Postdoctoral Researcher Dr Mike Tanner (Heriot Watt University), have completed the first steps in developing a camera that can ‘see’ through the human body. The camera is designed to help doctors track medical tools that are inserted into a patient in order to investigate a range of internal conditions. The new device is able to detect sources of light from inside, such as the illuminated tip of the endoscope’s long flexible tube. Until now, it has not been possible to track where an endoscope is located in the body in order to guide it to the right place without using X-rays or other expensive methods

Usually, light scatters or bounces off body tissue rather than travelling straight through. While this can reveal a wealth of information about internal structure it makes conventional through-tissue imaging practically impossible, as the scattering results in a blurred image and loss of information.

Taking advantage of single photon detection solves this problem. Not only does it give the camera a high sensitivity towards observing the small number of photons passing through tissue, but it also records the time they take to arrive onto the sensor. Light which is highly scattered travels a longer distance and therefore takes more time to reach the camera. Conversely, a small fraction of the light scatters relatively little and travels in a nearly direct (or ballistic) path to the camera, arriving much sooner. Operating the camera in a mode similar to a video camera, the early arrival of this so-called ‘ballistic light’ can be separated from the later, scattered light – a concept known as ‘ballistic imaging’. By detecting the first photons, it is possible to determine where the light source is located inside the body.

The prototype demonstrations have already shown that a point light source can be located through tissue approximately 20 cm thick under normal lighting conditions using the ballistic imaging technique. The camera will be further developed to enable clinicians to locate inserted medical devices at the bedside, visualising both the tip and length of the device.

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The camera is able to detect ‘ballistic photons’ – particles of light that pass through the body relatively unscattered (seen in the left-hand side image)

“This is an enabling technology that allows us to see through the human body. It has immense potential for diverse applications such as the one described in this work. The ability to see a device’s location is crucial for many applications in healthcare, as we move forwards with minimally invasive approaches to treating disease.”

Professor Kev Dhaliwal

“My favourite element of this work was the ability to work with clinicians to understand a practical healthcare challenge, then tailor advanced technologies and principles that would not normally make it out of a physics lab to solve real problems. I hope we can continue this interdisciplinary approach to make a real difference in healthcare technology.”

Dr Tanner

“Single-photon imaging technologies exhibit massive potential, and are an area where the UK leads the world. Proteus has uniquely brought together a multidisciplinary group of world-leading engineers, physicists, biologists, chemists and clinicians, to develop this potentially game-changing approach to medical imaging.”

Prof. Thomson

The article was published in Biomedical Optics Express, Vol. 8, Issue 9, pp.4077-4095 (2017)