Multimodal nonlinear microscopic investigations on head and neck squamous cell carcinoma: Toward intraoperative imaging

Background. Prognosis and appropriate treatment of head and neck squamous cell carcinoma (HNSCC) depend on the tumor type routinely derived by invasive histopathology. A promising non-invasive alternative is nonlinear optical imaging, which is capable of in vivo tissue visualization for tumor typing and grading. Methods. In this study coherent anti-Stokes Raman scattering (CARS), second harmonic generation (SHG) and two photon excited fluorescence (TPEF) were jointly employed to study the morphochemistry of tissue sections of three cases with HNSCC. Results. The tissue morphology has been visualized on single cell level to determine alterations of prognostic significance, e.g. cell density, nuclear to cytoplasm ratio and keratinization and information on the chemical composition of the tissue was derived, e.g. the distributions of lipids, collagen and autofluorophors. Conclusion. Nonlinear imaging provides a non-invasive optical biopsy of the epithelial layer. By integration into an operational microscope the multimodal information on tissue morphology can be used for surgical guidance.