Diagnostic potential of near-infrared Raman spectroscopy in the stomach: differentiating dysplasia from normal tissue

Abstract

Raman spectroscopy is a molecular vibrational spectroscopic technique that is capable of optically probing the biomolecular changes associated with diseased transformation. The purpose of this study was to explore near-infrared (NIR) Raman spectroscopy for identifying dysplasia from normal gastric mucosa tissue. A rapid-acquisition dispersive-type NIR Raman system was utilised for tissue Raman spectroscopic measurements at 785 nm laser excitation. A total of 76 gastric tissue samples obtained from 44 patients who underwent endoscopy investigation or gastrectomy operation were used in this study. The histopathological examinations showed that 55 tissue specimens were normal and 21 were dysplasia. Both the empirical approach and multivariate statistical techniques, including principal components analysis (PCA), and linear discriminant analysis (LDA), together with the leave-one-sample-out crossvalidation method, were employed to develop effective diagnostic algorithms for classification of Raman spectra between normal and dysplastic gastric tissues. High-quality Raman spectra in the range of 800 -1800 cm À1 can be acquired from gastric tissue within 5 s. There are specific spectral differences in Raman spectra between normal and dysplasia tissue, particularly in the spectral ranges of 1200 -1500 cm À1 and 1600 -1800 cm À1 , which contained signals related to amide III and amide I of proteins, CH 3 CH 2 twisting of proteins/nucleic acids, and the C ¼ C stretching mode of phospholipids, respectively. The empirical diagnostic algorithm based on the ratio of the Raman peak intensity at 875 cm À1 to the peak intensity at 1450 cm À1 gave the diagnostic sensitivity of 85.7% and specificity of 80.0%, whereas the diagnostic algorithms based on PCA-LDA yielded the diagnostic sensitivity of 95.2% and specificity 90.9% for separating dysplasia from normal gastric tissue. Receiver operating characteristic (ROC) curves further confirmed that the most effective diagnostic algorithm can be derived from the PCA-LDA technique. Therefore, NIR Raman spectroscopy in conjunction with multivariate statistical technique has potential for rapid diagnosis of dysplasia in the stomach based on the optical evaluation of spectral features of biomolecules.

In vivo early diagnosis of gastric dysplasia using narrow-band image-guided Raman endoscopy

“…The current results of in vivo gastric tissue Raman spectra are also similar to our previous observations of in vitro gastric tissue Raman spectra. [12][13][14] Therefore, the distinctive differences in in vivo Raman spectra between normal and dysplastic tissue confirm the potential role of Raman endoscopy for in vivo gastric precancer diagnosis at the molecular level.…”

“…More specifically, the decrease in Raman signals at 875 cm −1 ͑hy-droxyproline of collagen͒ may reflect cytoplasmic mucin depletion and the elevated concentration of metalloproteinase that cleaves collagen in the stroma layer of gastric dysplasia tissue. 13,14,22,23 In addition, the thickening of the epithelium associated with dysplastic progression can attenuate the excitation laser power and also obscure the collagen Raman emission from the deep basal membrane, 24,25 thereby resulting in an overall decrease of Raman intensity at 875 cm −1 from dysplasia tissue. The increase of Raman signals attributed to proteins ͑e.g., 1265, 1302, 1450, and 1655 cm −1 ͒ in gastric dysplasia may be associated with an increase in the metabolic activities ͑e.g., increased mitotic activities that include enzymes, hormones, etc.͒ as well as the increased hyperchromatism and the nucleic acids-to-cytoplasm ratio of dysplastic cells.…”

“…[4][5][6][7][8][9][10][11][12][13][14] These investigations show that specific spectral features of Raman spectra could be used to correlate with the molecular and structural changes of tissue associated with neoplastic trans-formation. Diagnostic sensitivities of ϳ85 to 95% and specificities of ϳ90 to 98% have been reported for differentiation between normal and pathological ͑e.g., dysplasia, adenocarcinoma͒ gastric tissues in vitro using Raman spectroscopic technique.…”

“…Diagnostic sensitivities of ϳ85 to 95% and specificities of ϳ90 to 98% have been reported for differentiation between normal and pathological ͑e.g., dysplasia, adenocarcinoma͒ gastric tissues in vitro using Raman spectroscopic technique. [12][13][14] However, to date, in vivo Raman studies for early diagnosis of gastric precancer and cancer have not been reported. In vivo Raman endoscopic applications have been limited not only by the difficulty of capturing inherently weak tissue Raman signals, but also by the relatively high speed of spectral acquisitions required in clinical settings.…”

Diagnostic model based on Raman spectra of normal, hyperplasia and prostate adenocarcinoma tissuesin vitro

“…PCA has been employed for spectral classification in a variety of diseases such as atherosclerosis and neoplasias, among others [9,10,[13][14][15]17,20,26,27,34,35]. With PCA, one could separate the relevant spectral information which is dependent on the composition of the material analyzed, i.e., a few variables, from the random, uncorrelated variations.…”