title: Discriminating adenocarcinoma from normal colonic mucosa through deconvolution of Raman spectra.
abstract: In this work, we considered the feasibility of Raman spectroscopy for discriminating between adenocarcinomatous and normal mucosal formalin-fixed colonic tissues. Unlike earlier studies in colorectal cancer, a spectral deconvolution model was implemented to derive spectral information. Eleven samples of human colon were used, and 55 spectra were analyzed. Each spectrum was resolved into 25 bands from 975 to 1720 cm(-1), where modes of proteins, lipids, and nucleic acids are observed. From a comparative study of band intensities, those presenting higher differences between tissue types were correlated to biochemical assignments. Results from fitting procedure were further used as inputs for linear discriminant analysis, where combinations of band intensities and intensity ratios were tested, yielding accuracies up to 81%. This analysis yields objective discriminating parameters after fitting optimization. The bands with higher diagnosis relevance detected by spectra deconvolution enable to confine the study to some spectral regions instead of broader ranges. A critical view upon limitations of this approach is presented, along with a comparison of our results to earlier ones obtained in fresh colonic tissues. This enabled to assess the effect of formalin fixation in colonic tissues, and determine its relevance in the present analysis.
authors.affiliation: IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Universidade do Porto, Departamento de Física e Astronomia da Faculdade de Cie^ncias, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
authors.forename: Patricia Cambraia
authors.initials: PC
authors.lastname: Lopes
authors.forename: Joaquim Agostinho
authors.initials: JA
authors.lastname: Moreira
authors.forename: Abilio
authors.initials: A
authors.lastname: Almeida
authors.forename: Artur
authors.initials: A
authors.lastname: Esteves
authors.forename: Ivan
authors.initials: I
authors.lastname: Gregora
authors.forename: Martin
authors.initials: M
authors.lastname: Ledinsky
authors.forename: Jose Machado
authors.initials: JM
authors.lastname: Lopes
authors.forename: Rui
authors.initials: R
authors.lastname: Henrique
authors.forename: Albino
authors.initials: A
authors.lastname: Oliveira
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry* / Q000175:diagnosis*; D003106:Colon / Q000737:chemistry*; D015179:Colorectal Neoplasms / Q000737:chemistry* / Q000175:diagnosis*; D016002:Discriminant Analysis; D005240:Feasibility Studies; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013059:Spectrum Analysis, Raman / Q000379:methods*