Near-infrared Raman spectroscopy for optical diagnosis in the stomach: identification of Helicobacter-pylori infection and intestinal metaplasia

Raman spectroscopy is a unique vibrational spectroscopic technique which can be used to probe biochemicals and biomolecular structures and conformations of tissues. The main objective of this study is to evaluate the feasibility of applying near-infrared (NIR) Raman spectroscopy for identification of nonneoplastic lesions (Helicobacter-pylori (Hp) infection, and intestinal metaplasia (IM)) highly associated with stomach cancer. A rapid-acquisition NIR Raman spectroscopic system was used for tissue Raman measurements at 785 nm excitation, and a total of 88 gastric tissue samples (57 normal; 11 Hp-infection; 20 IM) from 56 patients were measured. The principal components analysis (PCA) and linear discriminant analysis (LDA) techniques were implemented to develop effective diagnostic algorithms for classification of Raman spectra of different gastric tissue types. High-quality Raman spectra in the range of 800-1800 cm(-1) were acquired from gastric tissue within 5 seconds. Significant spectral differences in Raman spectra were observed among normal, Hp-infection and IM gastric tissue, particularly in the spectral ranges of 848-917, 960-1015, 1088-1133, 1206-1213, 1277-1313, 1395-1445, 1517-1549, 1607-1690, and 1714-1767 cm(-1) which contained signals related to proteins, lipids and porphyrin. PCA-LDA algorithms developed together with leave one patient out, cross validation technique yield diagnostic sensitivities of 91.7%, 80.0%, and 80.0%, and specificities of 80.0%, 100%, and 92.7%, respectively, for classification of normal, Hp-infection and IM gastric tissues. This work demonstrates the utility of NIR Raman spectroscopy for early diagnosis of Hp-infection and IM lesions in the gastric at the molecular level.