Nonlinear optical microscopy and microspectroscopy of oral precancers and early cancer

Multiphoton autofluorescence microscopy (MPAM) offers the ability to assess morphometry similar to that of pathologic evaluation as well as biochemical information from endogenous fluorophores which are altered with neoplastic transformation. In this study the spectroscopic properties of normal and neoplastic oral epithelium were evaluated toward the goal of identifying image/spectroscopic based indicators of neoplastic transformation using nonlinear optical microscopy. Results indicated measureable differences between normal, dysplasia, and SCC that could be helpful in delineating between the three conditions. In particular, a blue shift in autofluorescence emission was experienced for dysplasia relative to normal. However, in the case of SCC the epithelial emission experienced a significant red shift relative to both dysplasia and normal and displayed in an additional red peak that was not present in either normal or dysplastic mucosa. Results were consistent with published results for SCC in the single-photon literature. The study demonstrates that multiphoton autofluorescence spectroscopy may reveal features of oral mucosa that can be useful for differentiating normal and neoplastic mucosa. When combined with morphometry provided by MPAM, a potentially powerful technique for imaging of the oral cavity could be developed which provides both morphometric and spectroscopic information.