Transmission FT-IR Chemical Imaging on Glass Substrates: Applications in Infrared Spectral Histopathology

Fourier transform-infrared (FT-IR) chemical imaging in transmission mode has traditionally been performed on expensive mid-IR transparent windows such as barium/calcium fluoride, which are more fragile than glass, making preparation in the histopathology laboratories more cumbersome. A solution is presented here by using cheap glass substrates for the FT-IR chemical imaging, which has a high-wavenumber transmission window allowing measurement of the C-H, N-H, and O-H stretches occurring at ca. 2500-3800 cm(-1). The ''fingerprint" region of the IR spectrum occurring below 1800 cm(-1) is not obtainable; however, we demonstrate that a wealth of information is contained in the high wavenumber range using 71 patients on a breast tissue microarray (TMA) as a model for investigation. Importantly, we demonstrate that the tissue can be classified into four basic tissue cell types and that using just the epithelial cells, reasonable discrimination of normal and malignant tissue can be found.