An international team of researchers, including from the University of Adelaide, has reported a technological breakthrough for optical coherence tomography (OCT), which could revolutionise applications in ophthalmology, dermatology, cardiology, and the early detection of cancer.
Professor Kishan Dholakia, from the Centre of Light for Life and School of Biological Sciences at the University of Adelaide and the School of Physics and Astronomy at the University of St Andrews in the United Kingdom, said the study “breaks norms in optical imaging and I believe heralds a new path to recovering information at depth”.
The study authors said, “while advances in OCT have been spectacular, there are major drawbacks in terms of its resolving capacity at depth. It is often difficult to obtain discernible signals from OCT using light in the near-infrared range of the spectrum from depths beyond 1mm.
“OCT is a world-established method to gain useful information on human health – our approach can enhance this even further, Prof Dholakia said.
In a media release, the researchers explained that OCT relies on light being backscattered within the sample: this occurs when light passes between different layers of cells for example.
“It is like the well-known phenomenon in nature of light being scattered in a fog, consisting of droplets of water with a different refractive index than the surrounding air, which scrambles your view. The scattering makes it difficult to see through the fog.
Similarly, cells (membranes and even smaller parts) in biological tissue scatter light making imaging a challenge. In fact, to get a discernible signal from depths beyond 1mm of depth is enormously challenging due to several factors including signal from intervening tissue,” the researchers said.
Alternate View on Scattered Light
“The conventional wisdom is that the OCT signal is dominated by light has undergone a single backscattering event whereas light scattered (scrambled) many times is detrimental to image formation.”
The team said it discovered an alternate viewpoint – that selective collection of such scattered light can lead to improved image contrast at depth, particularly in highly scattering samples. Importantly they showed how this could be implemented in a facile manner with minimal additional optics by displacing the light delivery and collection paths.
Gavrielle Untracht, first author of the paper from the Technical University of Denmark (DTU), said: “The results of our study could be the start of a new way of thinking about OCT imaging. It’s so exciting to contribute to such a technological breakthrough in the well-established OCT field!”
Dr Peter Andersen, co-corresponding author from DTU, added: “The unique configuration, supported by our modelling, should redefine our view on OCT signal formation – and we can now use this insight to extract more information and to improve diagnosis of disease.”
The team believes its breakthrough is poised to defy convention and lead to a step change in recovering images at depth. The researchers have filed and been granted intellectual property rights in this area.
This cutting-edge development received funding from the UK and European Union, and the Australian Research Council (ARC).
The paper was published in Science Advances.1
1. Untracht, G.R., et al., Spatially offset optical coherence tomography: Leveraging multiple scattering for high-contrast imaging at depth in turbid media. Sci. Adv.9,eadh5435(2023).DOI:10.1126/sciadv.adh5435.