Raman Spectroscopy and Multiphoton Endomicroscopy for Labelfree Optical Diagnostics of Colon Cancer

Abstract: A successful diagnosis at the earliest, cellular stage of colon cancer is the key to combat this deadly disease. In this regard, the two labelfree optical technologies multiphoton endo-microscopy and Raman spectroscopy offer an immense potential. Multiphoton endo-microscopy uses autofluorescence and second harmonic generation in the samples for imaging tissue through histology like optional sectioning. The prototype of such an endoscope with a custom scan softwre was developed at the Institute of Bio-medical Technologies. in this master thesis, this scan softwre has been reworked and upgraded by new function, such as line averaging, a two-layer scan or the export as TIFF-files. Furthermore, a study on the bio-chemical changes during tumor development induces by ulcerative colitis in mice was performed using Raman spectroscopy. This technique is based on the inelastic scattering by molecules with certain rotational and vibrational energy bonds. It is molecule-specific but requires sophisticated processing algorithms to subtract the unwanted fluorescence background. A new measuring setup, a data processing algorithm and a complete statistical model were built and can be sued for more elaborate studies. The preliminary results suggest that the Raman signal is reliable and that the detected peaks match very well to the results of comparable studies. Unfortunately, the spectral differences between cancerous inflammatory and healthy tissue are not sufficient to enable an automatic differentiation. Finally the concept of a hybrid system is presented, combining multiphoton imaging with Raman spectroscopy to one single endoscope. Based on the exiting setups, the realization of such a hybrid system is feasible and might overcome most of the limitations preventing automatic cancer detection.