Raman spectroscopy in head and neck cancers: toward oncological applications

To test the spectral reproducibility of earlier findings under ex vivo conditions and to record good quality in vivo spectra in clinically implementable time in finger print region.

Spectra from 20 ex vivo tissues (10 normal and 10 tumor) were recorded using fiber optic probe coupled Raman spectrometer. In vivo spectra from 10 healthy volunteers were also recorded. Spectral differences were analyzed by PC-LDA method followed by validation by leave-one-out and test samples.

Spectral features of ex vivo normal tissue suggest predominant lipid features while protein is high in tumor conditions. Major spectral features of in vivo healthy volunteers share several commonalities with ex vivo normal tissues except minor differences in amide III region. Classification efficiency of 90, 85 and 96% for ex vivo tumor, normal and in vivo normal standard models, respectively after leave-one-out cross validation, was observed. Test prediction efficiency of standard models of ex vivo normal, ex vivo tumor and in vivo healthy volunteers were 82.5, 92.5 and 100%, respectively.

Our findings corroborate with the reported ex vivo and in vivo normal spectral features. Features of in vivo Raman spectra show strong similarities with ex vivo normal spectra minor but significant differences were also observed. Findings of this study indicate that with our instrument in vivo Raman spectra in finger print region can be recorded in short and clinically implementable time.