Near infrared Raman spectroscopic mapping of native brain tissue and intracranial tumors

Abstract

This study assessed the diagnostic potential of Raman spectroscopic mapping by evaluating its ability to distinguish between normal brain tissue and the human intracranial tumors gliomas and meningeomas. Seven Raman maps of native specimens were collected ex vivo by a Raman spectrometer with 785 nm excitation coupled to a microscope with a motorized stage. Variations within each Raman map were analyzed by cluster analysis. The dependence of tissue composition on the tissue type in cluster averaged Raman spectra was shown by linear combinations of reference spectra. Normal brain tissue was found to contain higher levels of lipids, intracranial tumors have more hemoglobin and lower lipid to protein ratios, meningeomas contain more collagen with maximum collagen content in normal meninges. One sample was studied without freezing. Whereas tumor regions did not change significantly, spectral changes were observed in the hemoglobin component after snap freezing and thawing to room temperature. The results constitute a basis for subsequent Raman studies to develop classification models for diagnosis of brain tissue.

Raman spectroscopy as a promising noninvasive tool in brain cancer detection

“…23 Kra®t et al acquired Raman spectra of major and minor brain lipids to obtain spectral pro¯les for qualitative as well as quantitative analyses and reported higher levels of lipids in normal tissues, and higher hemoglobin but lower lipid to protein ratios in intracranial tumors; thus RS could be used to distinguish normal and tumor tissues, and to determine the tumor type and grade. 24,25 Koljenovic et al also suggested that similar diagnostic information is present in both the¯ngerprint and the high wavenumber region. 26 In view of emerging information on relative lipid content in brain tumors, RS and mass spectrometry of lipid extracts from seven human tissue specimen was carried out by Kohler et al 27 Gliomas were characterized by increased water-and decreased lipid-content, and the results were similar to that observed in porcine tissues.…”

In vivo optical monitoring of tissue pathologies and diseases with vibrational contrast

“…On the other hand, spectroscopic techniques provide very high information content with typically low spatial sampling (a few points). Raman spectroscopy has a demonstrated diagnostic potential in oncology in vivo or ex vivo for a number of organs such as the colon [1], esophagus [2], stomach [3], breast [4,5], cervix [6,7], skin [8], bladder [9] and brain [10,11] to name only a few. The importance of such results are not only limited to the development of in vivo tools, but may also prove useful to improve the diagnostic accuracy of current methods, reduce inter-observer variability [12] and augment our understanding of carcinogenesis processes.…”

Identification of Pediatric Brain Neoplasms Using Raman Spectroscopy

“…In general, these studies had smaller sample sizes and compared only one or two types of tumor with normal brain tissue [13,14,16]. Other authors have used techniques to enhance the Raman signal for tumor identification [17]; however, these methods are unsuitable for future in vivo use because they require tagging with nonbiocompatible markers.…”

“…Several researchers have used Raman spectroscopy to identify changes in mouse and human adult brain tissues, from identifying the effects of radiation [10] to measuring different types of lipids present in the brain [11], establishing water concentration for the identification of edema (brain swelling) [12] and identifying cancer [13,14,15,16,17,18,19,20,21]. In general, these studies had smaller sample sizes and compared only one or two types of tumor with normal brain tissue [13,14,16].…”