Researchers have shown that existing optical fibre technology could be used to produce microscopic 3D images of tissue inside the body, which will pave the way towards 3D optical biopsies.
Optical biopsies, as compared to normal biopsies that require tissue to be harvested and sent off to a lab for analysis, enables clinicians to examine living tissue within the body in real-time.
As reported, the minimally-invasive approach uses ultra-thin microendoscopes to peer inside the body for diagnosis or during surgery, but normally produces only two-dimensional images.
RMIT University led the research that revealed the 3D potential of the existing microendoscope technology.
Using microendoscopes
The new technique uses a light field imaging approach to produce microscopic images in stereo vision, similar to watching 3D movies while wearing 3D glasses.
Stereo vision is the natural format for human vision where people look at an object from two different viewpoints and process these in the brains to perceive depth.
It turns out these optical fibres work similarly, naturally capturing images from multiple perspectives, giving depth perception at the microscale.
The approach can process all those microscopic images and combine the viewpoints to deliver a depth-rendered visualisation of the tissue being examined – an image in three dimensions.
How it works
It was discovered that optical fibre bundles transmit 3D information in the form of a light field.
The challenge for the researchers was how to harness the recorded information, unscramble it and produce an image that makes sense.
Fortunately, the technique developed was able to overcome the challenges. Even better, the technique works even when the optical fibre bends and flexes, which is essential for clinical use in the human body.
The approach draws on principles of light field imaging, where traditionally, multiple cameras look at the same scene from slightly different perspectives.
Light field imaging systems measure the angle of the rays hitting each camera, recording information about the angular distribution of light to create a “multi-viewpoint image”.
A key observation made is that the angular distribution of light is subtly hidden in the details of how these optical fibre bundles transmit light.
The fibres essentially ‘remember’ how light was initially sent in. The pattern of light at the other side depends on the angle at which light entered the fibre.
Mathematical framework
A mathematical framework was developed with this in mind in order to relate the output patterns to the light ray angle.
By measuring the angle of the rays coming into the system, the 3D structure of a microscopic fluorescent sample can be figured out by using the information in a single image.
Hence, the optical fibre bundle acts like a miniaturised version of a light field camera.
The approach they are using is fully compatible with the optical bundles that are already in clinical use. Therefore, it is possible that 3D optical biopsies could be a reality sooner than later.
In addition to medical applications, the ultra-slim light field imaging device could potentially be used for in vivo 3D fluorescence microscopy in biological research.
The study was made in collaboration with CNBP colleagues at Macquarie University and the Centre for Micro-Photonics at Swinburne University.
