Evaluation of a Confocal Raman Probe for Pathological Diagnosis during Colonoscopy

AIM: Raman spectroscopy of human tissue can provide a unique biochemical 'fingerprint' that alters with disease progression. Light incident on tissue is scattered and may be altered in wavelength which can be represented as a Raman spectrum. A confocal fibreoptic Raman probe designed to fit down the accessory channel of a colonoscope has been constructed. This in vitro study evaluated the accuracy of pathological diagnosis in the colon using probe-based Raman spectroscopy.

METHODS: Biopsy samples were collected at colonoscopy, snap frozen and stored at -80°C. Raman spectra with 10s and 1s acquisition periods were measured with the probe tip in contact with the mucosal surface of thawed specimens. Mathematical modelling using principal component followed by linear discriminant analysis was used to correlate Raman spectra with histopathological diagnoses.

RESULTS: 375 Raman spectra were measured from a total of 356 colon biopsies from 177 patients (81, 79, 92, 64 and 40 biopsies of normal colon mucosa, hyperplastic polyps, adenomatous polyps, adenocarcinoma and ulcerative colitis respectively). Spectral classification accuracies comparing pathology pairs ranged from 72.1% to 95.9% and 61.5% to 95.1% with 10s and 1s acquisitions respectively. For a three group model of normal, adenomatous and adenocarcinoma tissue, accuracies were 74.1% and 63.5% for 10s and 1s acquisitions.

CONCLUSION: The confocal Raman probe system can distinguish between different colorectal pathologies. The probe has potential to establish Raman spectroscopy as a clinical tool for instant diagnosis at colonoscopy. This article is protected by copyright. All rights reserved.