Raman spectroscopy has been proven to have tremendous potential as biomedical analytical tool for spectroscopic disease diagnostics. The use of fiberoptic coupled Raman spectroscopy systems can enable in-vivo characterization of suspicious lesions. However, Raman spectroscopy has the drawback of rather long acquisition times of several hundreds of milliseconds which makes scanning of larger regions quite challenging. By combining Raman spectroscopy with a fast imaging technique this problem can be alleviate in part. Fluorescence lifetime imaging (FLIm) offers a great potential for such a combination. FLIm can allow for fast tissue area pre-segmentation and location of the points for Raman spectra acquisition. Here, we introduce an optical fiber probe combining FLIm and Raman spectroscopy with an outer diameter of 2 mm. Fluorescence is generated via excitation with a fiber laser at 355 nm. The fluorescence emission is spectrally resolved using a custom-made wavelength-selection module (WSM). The Raman excitation power at 785 nm was set to 50 mW for the in-vivo measurements to prevent sample drying. The lateral probe resolution was determined to be <250 μm for both modalities. This value was taken as step size for several raster scans of different tissue types which were conducted to show the overlap of both modalities under realistic conditions. Finally the probe was used for in vivo raster scans of a rat’s brain and subsequently to acquire FLIm guided Raman spectra of several tissues in and around the craniotomy.
Sebastian Dochow, Dinglong Ma, Ines Latka, Thomas Bocklitz, Brad Hartl, Julien Bec, Hussain Fatakdawala, Sebastian Wachsmann-Hogiu, Eric Marple, Kirk Urmey, Michael Schmitt, Laura Marcu, and Jürgen Popp, "Combined fiber probe for fluorescence lifetime and Raman spectroscopy (Conference Presentation)," Proc. SPIE 9698, Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XIV, 969806 (Presented at SPIE BiOS: February 14, 2016; Published: 27 April 2016); https://doi.org/10.1117/12.2214151.4828178761001.
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