title: Discriminating neoplastic and normal brain tissues in vitro through Raman spectroscopy: a principal components analysis classification model.
abstract: OBJECTIVE
  Because of their aggressiveness, brain tumors can lead to death within a short time after diagnosis. Optical techniques such as Raman spectroscopy may be a technique of choice for in situ tumor diagnosis, with potential use in determining tumor margins during surgery because of its ability to identify biochemical changes between normal and tumor brain tissues quickly and without tissue destruction.
  
  
  METHODS
  In this work, fragments of brain tumor (glioblastoma, medulloblastoma, and meningioma) and normal tissues (cerebellum and meninges) were obtained from excisional intracranial surgery and from autopsies, respectively. Raman spectra (dispersive spectrometer, 830 nm 350 mW, 50 sec accumulation, total 172 spectra) were obtained in vitro on these fragments. It has been developed as a model to discriminate between the spectra of normal tissue and tumors based on the scores of principal component analysis (PCA) and Euclidean distance.
  
  
  RESULTS
  ANOVA indicated that the scores of PC2 and PC3 show differences between normal and tumor groups (p<0.05) which could be employed in a discrimination model. PC2 was able to discriminate glioblastoma from the other tumors and from normal tissues, showing featured peaks of lipids/phospholipids and cholesterol. PC3 discriminated medulloblastoma and meningioma from normal tissues, with the most intense spectral features of proteins. PC3 also discriminated normal tissues (meninges and cerebellum) by the presence of cholesterol peaks. Results indicated a sensitivity and specificity of 97.4% and 100%, respectively, for this in vitro diagnosis of brain tumor.
  
  
  CONCLUSIONS
  The PCA/Euclidean distance model was effective in differentiating tumor from normal spectra, regardless of the type of tissue (meninges or cerebellum).
authors.affiliation: 1 Biomedical Engineering Institute, Universidade Camilo Castelo Branco - UNICASTELO , Parque Tecnológico de São José dos Campos, São José dos Campos, SP, Brazil .
authors.forename: Ricardo Pinto
authors.initials: RP
authors.lastname: Aguiar
authors.forename: Landulfo
authors.initials: L
authors.lastname: Silveira
authors.forename: Edgar Teixeira
authors.initials: ET
authors.lastname: Falcão
authors.forename: Marcos Tadeu Tavares
authors.initials: MT
authors.lastname: Pacheco
authors.forename: Renato Amaro
authors.initials: RA
authors.lastname: Zângaro
authors.forename: Carlos Augusto
authors.initials: CA
authors.lastname: Pasqualucci
mesh_terms: D001923:Brain Chemistry; D001932:Brain Neoplasms / Q000737:chemistry*; D003661:Decision Support Techniques; D006801:Humans; D066298:In Vitro Techniques; D013059:Spectrum Analysis, Raman