Discrimination of brain tumours and dysplastic tissues through multimodal fibre-probe spectroscopy

Optical spectroscopy is a fast, label-free and non-invasive method for analysing tissue composition and, thus, has the potential for improving standard diagnostic capabilities. This is particularly relevant for brain surgery due to the lack of contrast between diseased tissues (e.g. malformations and tumours) and the surrounding brain. In this study, we used an optical fibre-probe system combining multiple spectroscopic techniques for analysing ex vivo human brain biopsies taken from both tumour and dysplastic tissues. Specifically, the probe - based on a fibre-bundle with optical fibres of various size and properties - allowed performing spectroscopic measurements based on fluorescence, Raman, and diffuse reflectance spectroscopy. Two visible laser diodes were used for fluorescence spectroscopy, a laser diode emitting in the NIR was used for Raman spectroscopy, and a fibre-coupled halogen lamp for diffuse reflectance. All spectral recordings were done within 30 minutes from surgical resection, and optical inspection required less than 2 minutes for each sample. The recorded data were analysed using Principal Component Analysis (PCA) for obtaining an automated classification of the examined samples based on the intrinsic spectral information provided by all three techniques. The presented method demonstrated high sensitivity and specificity in discriminating different tissue types in good agreement with histopathological examination. Furthermore, we found that the multimodal approach is crucial for improving diagnostic capabilities beyond what can be achieved from individual techniques.