Interpreting CARS images of tissue within the C-H-stretching region.

Single band coherent anti-Stokes Raman scattering (CARS) microscopy is one of the fastest implementation of nonlinear vibrational imaging allowing for video-rate image acquisition of tissue. This is due to the large Raman signal in the C-H-stretching region. However, the chemical specificity of such images is conventionally assumed to be low. Nonetheless, CARS imaging within the C-H-stretching region enables detection of single cells and nuclei, which allows for histopathologic grading of tissue. Relevant information such as nucleus to cytoplasm ratio, cell density, nucleus size and shape is extracted from CARS images by innovative image processing procedures. In this contribution CARS image contrast within the C-H-stretching region is interpreted by direct comparison with Raman imaging and correlated to the tissue composition justifying the use of CARS imaging in this wavenumber region for biomedical applications.