Raman difference spectroscopy: a non-invasive method for identification of oral squamous cell carcinoma

Abstract

The feasibility of shifted-excitation Raman difference spectroscopy (SERDS) as a label-free and non-invasive technique for an objective diagnosis of oral cancer (OSCC) was investigated by analyzing 12 ex vivo OSCC samples. 72 mean SERDS spectra from each three physiological tissue points and pathological lesions were correlated with the histo-pathological diagnosis. Principal component analysis (PCA) and linear discriminant analysis (LDA) showed excellent results with an area under the curve of 94.5% and a classification error of 9.7% (sensitivity: 86.1%; specificity: 94.4%). The SERDS Raman spectra of malignant and benignant tissues were discriminable with respect to the spectral features of proteins, lipids and nucleic acids. The presented method is capable of a highly accurate identification of OSCC. These findings suggest a high validity and reproducibility of SERDS combined with PCA and LDA analysis regarding oral cancer tissue.

Keywords: (170.0170) Medical optics and biotechnology; (170.3890) Medical optics instrumentation; (170.5660) Raman spectroscopy; (170.6935) Tissue characterization.

Fig. 1

Raman spectroscopic setup a) excitation diode laser (variable wavelength), b) excitation glass fiber, c) lens, d) lens f = 100 mm, e) dichroic beam splitter 800nm, f) biological tissue, g) long pass filter 785 nm, h) detection glass fiber bundle, i) spectrometer.

Fig. 2

Histological confirmation of each measurement point (2,5x magnification / haematoxylin eosin stained slide) a) physiological tissue b) pathological OSCC lesion.

Fig. 3

Spectra processing procedure.

Fig. 4

Receiver operating characteristic (ROC) curve representing the diagnostic accuracy with an area under the curve (AUC) of 0.945.

Fig. 5

Assigment of spectral features of proteins, lipids and nucleic acids to the ones of pathological and physiological oral tissue.