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  • Hollow-core Photonic Crystal Fibre-based Needle Probes for Raman Spectroscopy of Biological Tissue

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  • The development of medical imaging and other techniques for accurate in vivo cancer diagnosis and monitoring can be less invasive and detect disease in an earlier stage than internal biopsies. Earlier detection is important, to avoid metastasis. Cancers are masked by overlying tissue which is not easily penetrated by light but can be overcome by needle probes. This project is to undertake the design, fabrication, characterization, and modelling of confocal needle probes for imaging and characterizing biological tissue in vivo using Raman spectroscopy. With Raman imaging, the chemical composition of a biological sample can be accurately measured, making it an excellent technique to diagnose all types of diseases in vivo with probes. Imaging Raman spectroscopy at high resolution through probes less than 310 µm in diameter has yet to be demonstrated.

     

    In this project, novel probes were designed with smaller diameters, less than 150 µm, by using hollow-core fibres (HCF) and a Raman spectroscopy measurement system with filters to reduce and eliminate unwanted Raman and Rayleigh scattering. The probes were fabricated with commercially available HCF, collapsed by heat into a ball lens using a fusion splicer and then fused to an optical fibre patch cord for characterization. Probes with ball lenses of different diameters were prepared and characterized using a beam profiler to determine the optimum size of the ball lens. The diameters of the ball lenses ranged from 147 to 264 ± 5 µm and their corresponding spot sizes ranged from 5.0 to 18.5 µm in the x-direction, and 3.4 to 21.1 µm in the y-direction, with the optimal probe having the smallest spot size and highest resolution.

     

    In conclusion, HCF probes that could be used in needles with a diameter of less than 0.31 mm were designed which could lead to imaging the chemical composition of a biological sample in vivo using Raman spectroscopy. In turn, this could significantly advance our understanding and treatment of diseases that prior to this technology would not have been accessible.

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