Near-Infrared Raman Spectroscopy for In Vitro Detection of Cervical Precancers

Abstract

In this study, we investigate the potential of near-infrared Raman spectroscopy to differentiate cervical precancers from normal tissues, inflammation and metaplasia and to differentially diagnose low-grade and high-grade precancers. Near infrared Raman spectra were measured from 36 biopsies from 18 patients in vitro. Detection algorithms were developed and evaluated relative to histopathologic examination. Algorithms based on empirically selected peak intensities, ratios of peak intensities and a combination of principal component analysis for data reduction and Fisher discriminant analysis for classification were investigated. Spectral peaks were tentatively identified from measured spectra of potential chromophores. Empirically selected normalized intensities can differentiate precancers from other tissues with an average sensitivity and specificity of 88 +/- 4% and 92 +/- 4%. Ratios of unnormalized intensities can differentiate precancers from other tissues with a sensitivity and specificity of 82% and 88% and high-grade from low-grade lesions with a sensitivity and specificity of 100%. Using multivariate methods, intensities at eight frequencies can be used to differentiate precancers from all other tissues with a sensitivity and specificity of 82% and 92% in an unbiased test. Raman algorithms can potentially separate benign abnormalities such as inflammation and metaplasia from precancers. Comparison of tissue spectra to published and measured chromophore spectra indicate that the most likely primary contributors to the tissue spectra are collagen, nucleic acids, phospholipids and glucose 1-phosphate. These results suggest that near-infrared Raman spectroscopy can be used for cervical precancer diagnosis and may be able to accurately separate samples with inflammation and metaplasia from precancer.

The use of Raman spectroscopy to identify and grade prostatic adenocarcinoma in vitro

“…(Bakker Schut et al, 1997) and cervix (Mahadevan-Jansen et al, 1998). These findings provide an insight into the type of molecular differences, which allow the technique to differentiate between the different pathologies.…”

“…Raman spectroscopy is an optical technique that utilises molecular-specific, inelastic scattering of light photons to interrogate biological tissues (Mahadevan-Jansen et al, 1998). When tissue is illuminated with laser light, photons interact with intramolecular bonds present within the tissue.…”

Raman spectroscopy can differentiate malignant tumors from normal breast tissue and detect early neoplastic changes in a mouse model

“…Other studies have also shown the ability of Raman spectroscopy to accurately classify diseased tissue in brain, 16,17 skin, [18][19][20][21][22][23][24] cervix, [25][26][27] breast, 1,2,9,10,28-33 and other organs. 8,11,[34][35][36][37][38][39][40][41][42][43][44] Our data is confirmatory, and, in addition, demonstrates changes in the tumor bed, which probably represent the detection of chemical signs of preneoplastic changes.…”

“…The reason that some spectra from a sample are different is that all samples contain a variety of tissues, such as blood vessels, residual normal organ tissue, and fat. 25,26 For example, Figure 3 shows the Raman spectra of six different points on the same tumor sample. There are clear differences in the spectral (and therefore chemical) compositions between points b, c, d, e, and a and f, which may reflect two trapped normal components within a tumor sample.…”

A study examining the effects of tissue processing on human tissue sections using vibrational spectroscopy

“…Raman however, has the advantage of minimal interference from water so is a good choice for biological samples with a view to in vivo measurements. Some of the tissue types examined by various groups include; cervical [2][3][4], breast [5][6][7], skin [8][9][10][11][12], lung [13], brain [14,15] bladder [16], esophagus [17][18][19], colon [20], liver [21,22], thyroid [23] and prostate [24,25]. A variety of different methods of sample preparation have been employed in these studies, such as; fresh, frozen, airdried, formalin-fixed and de-waxed formalin fixed paraffin preserved (FFPP) tissue sections.…”