Mid-Infrared fiber-optics leading the future for early cancer detection
Ashley Collier, Corporate Communications Manager, Optica
In her current role at the University of Nottingham, UK, Professor Angela B. Seddon leads the Mid-Infrared Photonics Group. Seddon and her colleagues operate a world-class facility for fabricating and characterizing mid-infrared fiber optics, chips, and devices. Her current research emphasizes real-time mid-infrared medical sensing, imaging, and endoscopy for early cancer detection. At Optica’s recent Laser Congress, Seddon's plenary presentation detailed a new 'window of opportunity' for real-time mid-infrared medical sensing, imaging, and endoscopy for early cancer detection.
First discovered in 1800 by German-born, England’s Royal Astronomer William Herschel, mid-infrared light has practical uses for humanity, including modern medicine and astronomy. Launched on 25 December 2021, the James Webb Space Telescope (JWST) has revealed images of the universe beyond imagination. Seddon noted JWST multi-wavelength near- and mid-infrared NASA imaging of galaxy clusters far into the universe with impressive accuracy. Seddon stated, "using mid-infrared light, scattering is lowered due to the longer wavelength and molecular absorption made possible, already revealing the presence of carbon dioxide on an exoplanet."
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According to the International Organization for Standardization (ISO), the mid-infrared (MIR) wavelength region is identified as 3 µm to 50 µm. Seddon explained that molecular species emit or absorb mid-infrared energy when their vibrational state changes. Symmetric stretching, bending, and asymmetric stretching are the three fundamental vibrations of molecules.
In her presentation, Seddon noted a new type of mid-infrared imaging demonstrated in 2016 (Nallala et al. Analyst, see image). This development is working to shape the future of pathology by achieving chemical mapping, instead of visible topology as in the current ‘Gold Standard’ histopathology. Seddon described the importance of the resolution change of oversampled excised tissue. "By oversampling, we can get to the resolution of one micron, which is like the optical microscopy used today to pick up tissue problems," she added.
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Seddon believes that future mid-infrared pathology will enable high specificity and high sensitivity for the discrimination of diseases. She emphasized that high specificity and sensitivity can discriminate diseases like cancer. The advantage of direct MIR molecular sensing is that it does not need labeling or fluorescent tags, is highly contrasted, quantitative, and is widely applicable.
Seddon credits her research is motivated by the UK's leading cancer charity, Cancer Research UK. "Frighteningly, Cancer Research reported in 2015 that 50% of us in the UK will be diagnosed with cancer, mainly basal cell carcinomas, which is not movable around the body," said Seddon. She is also motivated to change the "Gold Standard” of today's imaging approach. Today, histopathology is the gold standard of treatment for cancer detection, which requires clinicians to wait a couple of weeks to view the excise tissue samples that have been dye-stained and studied by pathologists to confirm any suspected diseases. Seddon and her colleagues propose an unconventional method to detect cancer using mid-infrared detection. This alternative, optical biopsy in-situ, will detect cancer through internal tissue. As opposed to performing biopsies, cancer could be seen internally for instance within the esophagus with immediate feedback on cancer detection. Similarly, Seddon proposed that the same practice be used with early mid-infrared light imaging of skin moles in-vivo to catch skin cancer early, eliminating hospital visits.
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"Practical deployment of the mid-infrared optical biopsy requires the means to generate bright, mid-infrared light across a broad spectrum and to rout it to where it's needed," said Seddon. She and her colleagues aim to attain this through the focused development of MIR fiber-optic devices and systems which are robust, functionally designed, safe, compact, and cost-effective. The proposed mid-infrared endoscopy requires passive and nonlinear glass fiber to rout and produce broadband MIR light and luminescent fiber to pump this. Seddon noted MIR transparent chalcogenide glasses exhibit weaker chemical bonding than silica glasses; however, unlike fluoride glasses, chalcogenide glasses are exceptionally stable in water, liquid and vapor, and are not oxidized in an ambient atmosphere.
As chemical vapor diposition (CVD) routes are not possible due to widely different vapour pressures of chalcogenide glass formulations, through glass batching, Seddon and her team make glasses conventionally. After glass batching, the process proceeded with sealing the batch into melt containment and quenching the melt. Seddon explained, "instead of using chemical vapor deposition to make optical preforms, we developed extrusion." Seddon's team successfully created sulfide fiber, selenide fiber, small core (down to 4 microns’ core diameter) and large core fiber. Supercontinuum light generation relies on ultrashort light pulses and nonlinear material-generating effects readily attained in chalcogenide glass fiber. Her Group recently announced the first fiber laser operating beyond 4 microns for pumping supercontinua (2021, Optics Letters).
In closing, Seddon believes this advancement of mid-infrared light has the ability to chemically map tissue and distinguish between normal and cancerous tissue without long-waited biopsies and hospital visits. "I assure you, from the results of many other groups of scientists, mid-infrared can distinguish normal and cancerous tissue to high specificity and sensitivity," she added. As mid-infrared optical fibers continue to lead the future as light conduits and light producers, she believes the prospects of a new mid-infrared endoscopy based on mid-infrared optical fibers shine brightly in the future.
