FTIR, Raman, and CARS microscopic imaging for histopathologic assessment of brain tumors

Abstract

The contribution demonstrates how the molecular contrast of Fourier transform infrared (FTIR), Raman and coherent anti-Stokes Raman scattering (CARS) microscopic imaging can be applied for the histopathological assessment of brain tumors. Human brain tissue specimens were obtained from patients undergoing neurosurgery. Thin sections of control brain tissue from an epilepsy patient and tumor tissue from a meningioma patient were prepared on calciumfluoride slides which were appropriate substrates for data acquisition in transmission and reflection mode. All CARS images correlate well with the FTIR and Raman images. Whereas CARS images were collected within seconds, exposure times were minutes for FTIR imaging and hours for Raman imaging. CARS images in the interval 2750-3000 cm^-1 mainly probed spectral contributions of lipids which are important diagnostic markers of brain tumors. It was demonstrated that the CARS profile in the interval 2750-3000 cm^-1 differed between the control sample and meningioma. Full spectral information could be extracted from Raman and FTIR images that enabled to distinguish different tissue types in brain tumors. Based on the current results we suggest a complementary application of FTIR, Raman and CARS imaging. FTIR and Raman imaging defines spectral regions and spectral markers that are essential for tissue classification. CARS images at different Stokes shifts or in the multiplex mode probe these spectral descriptors at video-time frame rates.