Combined autofluorescence and diffuse reflectance spectroscopy for rapid metabolic and vascular characterizations of orthotopic tongue tumors <i>in vivo</i>

Precise label-free quantification of tissue metabolic and vascular dynamics in vivo represents a critical challenge for cancer therapy prediction and longitudinal treatment assessment. In this study, we demonstrated a portable autofluorescence and diffuse reflectance spectroscopy device along with novel spectroscopic algorithms to quantify tissue vascular and metabolic parameters of orthotopic head and neck cancer models in vivo . Tissue-mimicking phantom studies were used to verify the dual-modal optical spectroscopy and easy-to-use spectroscopic algorithms for rapid and accurate estimation of tissue oxygen saturation, total hemoglobin contents, and intrinsic optical redox ratio. Animal studies were conducted to demonstrate the feasibility of our technique for rapid functional characterization of small tongue tumors in vivo . Our phantom studies demonstrated that our dual-modal optical spectroscopy, along with novel spectroscopic algorithms, can accurately quantify tissue vascular and metabolic parameters in near real-time. Our in vivo animal studies captured reduced total hemoglobin contents and lower oxygen saturation in orthotopic tongue tumors compared to normal tongue tissues. Our data also showed that mouse tongue tumors with different radiation sensitivities had significantly different intrinsic optical redox ratios. Additionally, we observed elevated Protoporphyrin IX levels in tongue tumors compared with normal tongue tissues. These results demonstrated the potential of our portable dual-modal optical spectroscopy to noninvasively evaluate tumor metabolism and its vascular microenvironment in tongue cancer models for future oral cancer research.