Tissue classification using a fiber probe for combined Raman, fluorescence and reflectance spectroscopy

A multimodal spectroscopic fiber probe for combined Raman, fluorescence and reflectance measurements was designed, developed and used for tissue diagnostics. Two visible laser diodes emitting in the visible range, a laser diode emitting in the NIR, and a halogen lamp were respectively used for fluorescence, Raman and reflectance spectroscopy. The probe was based on a custom fiber bundle, equipped with various types of fibers for exciting and detecting the signals of interest. Fluorescence, Raman and reflectance spectra were acquired using the same detection unit, based on a cooled CCD camera, connected to a spectrograph. The probe was successfully employed for diagnostic purposes on various tissues in a good agreement with common routine histology. This study included skin, brain and bladder tissues and in particular the classification of: malignant melanoma against melanocytic lesions and healthy skin; urothelial carcinoma against healthy bladder mucosa; brain tumor against dysplastic brain tissue. The diagnostic capabilities were determined using a cross-validation method with a leave-one-out approach, finding very high sensitivity and specificity for all the examined tissues. The obtained results demonstrated that the multimodal approach is crucial for improving diagnostic capabilities, as well as for performing tumor grading. The system presented here can improve diagnostic capabilities on a broad range of tissues and has the potential of being used for endoscopic inspections in the near future.