Diffuse reflectance spectroscopy for optical characterizations of orthotopic head and neck cancer models in vivo

We demonstrated an easy-to-build, portable diffuse reflectance spectroscopy device along with a Monte Carlo inverse model to quantify tissue absorption and scattering-based parameters of orthotopic head and neck cancer models in vivo. Both tissue-mimicking phantom studies and animal studies were conducted to verify the optical spectroscopy system and Monte Carlo inverse model for the accurate extraction of tissue optical properties. For the first time, we reported the tissue absorption and scattering coefficients of mouse normal tongue tissues and tongue tumor tissues. Our in vivo animal studies showed reduced total hemoglobin concentration, lower tissue vascular oxygen saturation, and increased tissue scattering in the orthotopic tongue tumors compared to the normal tongue tissues. Our data also showed that mice tongue tumors with different sizes may have significantly different tissue absorption and scattering-based parameters. Small tongue tumors (volume was ∼60 mm³) had increased absorption coefficients, decreased reduced-scattering coefficients, and increased total hemoglobin concentrations compared to tiny tongue tumors (volume was ∼18 mm³). These results demonstrated the potential of diffuse reflectance spectroscopy to noninvasively evaluate tumor biology using orthotopic tongue cancer models for future head and neck cancer research.