Mapping of healthy oral mucosal tissue using diffuse reflectance spectroscopy: ratiometric-based total hemoglobin comparative study

The objective of this study is to clinically evaluate the diffuse reflectance spectroscopy (DRS) ratiometric method for differentiation of normal oral mucosal tissues with different histological natures and vascularizations in the oral cavity. Twenty-one healthy patients aged 20–44 years were diagnosed as healthy and probed with a portable DRS system. Diffuse reflectance spectra were recorded in vivo in the range (450–650 nm). In this study, the following three oral mucosal tissues were considered: masticatory mucosa, lining mucosa, and specialized mucosa. Spectral features based on spectral intensity ratios were determined at five specific wavelengths (512, 540, 558, 575, and 620 nm). Total hemoglobin based on spectral ratios for the three anatomical regions have also been evaluated. The three studied groups representing different anatomical regions in the oral cavity were compared using analysis of variance and post hoc least significant difference tests. Statistical analysis showed a significant difference in the mean of diffuse spectral ratios between the groups (P < 0.05). Post hoc test detected significant difference between masticatory mucosa group and lining mucosa group (P < 0.05) and between masticatory mucosa group and specialized mucosa group (P = 0.000, at ratio 558/620 and P = 0.000, at ratio 575/620). Significant difference was also found between the lining mucosa group and specialized mucosa group (P = 0.000, at ratio 512/558 and P = 0.000, at ratio 512/575). It has also been shown that spectral ratios at wavelengths 558, 575, and 620 nm reveal the greatest difference among the main oral sites in terms of total hemoglobin content. Diffuse reflectance spectroscopy might be used for creating a DRS databank of normal oral mucosal tissue with specific spectral ratios featuring the total hemoglobin concentrations. That would further enhance the discrimination of oral tissue for examining the histological nature of oral mucosa and diagnosis of early precancerous changes in the oral cavity based on non-invasive monitoring of neovascularization.