A comparison of Raman, FTIR and ATR-FTIR micro spectroscopy for imaging human skin tissue sections

Raman and infrared absorption spectroscopies are compared for the analysis of human hand skin tissue sections. The tissue sections have been formalin fixed and paraffin processed, and subsequently dewaxed. Fourier Transform Infrared (FTIR) spectra are preprocessed using the resonant Mie-extended multiplicative scattering algorithm to remove spectral artefacts. FTIR images of resolution 4 cm^-1, analysed using K-means cluster analysis, reveal the double layer structure of the dermis and epidermis, but no further layer differentiation is achieved using the higher spatial resolution of the Attenuated Total Reflection imaging or improved spectral resolution of 2 cm ^-1. At comparable spectral and spatial resolutions and measurement on the same samples, Raman scattering produces spectra of significantly higher spectral detail and can differentiate the stratum corneum from the underlying epithelial layer, and, in the absence of melanin in an artificial skin model, can further differentiate the basal layer from the overlying epithelium. The differences in the performance of the techniques are therefore not instrumentational and are discussed in terms of the technological and fundamental differences between the two complementary techniques.