Scientists have developed a camera that can detect sources of light from inside the body, an advance that could help doctors track medical tools inserted into patients.
Led by Dr Mike Tanner, the EPSRC-funded Proteus team has developed a device capable of detecting sources of light that might include the illuminated tip of an 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 costly methods.
Light usually scatters off body tissue rather than travelling straight through it, which is helpful for unveiling information about internal structures. Consequently, light scattering 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 is said to solve this problem by giving the camera a high sensitivity towards observing the small number of photons passing through tissue and recording the time they take to arrive onto the sensor.
According to the Proteus team, light which is highly scattered travels a longer distance and takes longer to reach the camera. Conversely, a small fraction of the light scatters relatively little and travels in a nearly direct – 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.
Prototype demonstrations have shown that a point light source can be located through tissue approximately 20cm 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.
Prof Kev Dhaliwal, of Edinburgh University, said: “This is an enabling technology that allows us to see through the human body. 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.”
The team’s results are published in Biomedical Optics Express.