Ultraviolet laser‐induced fluorescence of colonic tissue: Basic biology and diagnostic potential

Abstract

Laser-induced fluorescence (LIF) of colonic tissue was examined both in vitro and in vivo to assess the ability of the technique to distinguish neoplastic from hyperplastic and normal tissue and to relate the LIF spectra to specific constituents of the colon. Spectra from 86 normal colonic sites, 35 hyperplastic polyps, 49 adenomatous polyps, and 7 adenocarcinomas were recorded both in vivo and in vitro. With 337-nm excitation, the fluorescence spectra all had peaks at 390 and 460 nm, believed to arise from collagen and NADH, and a minimum at 425 nm, consistent with absorption attributable to hemoglobin. The spectra of colonic tissue recorded both in vivo and in vitro are different, primarily in the NADH fluorescence component, which decays exponentially with time after resection. When normal colonic tissue is compared to hyperplastic or adenomatous polyps, the predominant changes in the fluorescence spectra are a decrease in collagen fluorescence and a slight increase in hemoglobin reabsorption. A multivariate linear regression (MVLR) analysis was used to distinguish neoplastic tissue from non-neoplastic tissue with a sensitivity, specificity, predictive value positive, and predictive value negative toward neoplastic tissue of 80%, 92%, 82%, and 91%, respectively. When the MVLR technique was used to distinguish neoplastic polyps from non-neoplastic polyps, values of 86%, 77%, 86%, and 77% respectively, were obtained. The data suggest that the LIF measurements sense changes in polyp morphology, rather than changes in fluorophores specific to polyps, and it is this change in morphology that leads indirectly to discrimination of polyps.

Discrimination of normal, inflammatory, premalignant, and malignant oral tissue: A Raman spectroscopy study

“…Many cell surface proteins, enzymes, hormones, etc., are also produced in larger amounts under disease conditions. 33 On the other hand, it is found that collagen fluorescence in oral tissue is reduced in malignancy, [36][37][38] which is attributed to both collagen lysis as well as thickening of the epithelial layer. It may therefore be thought that the Raman spectrum of normal tissue, which is basically mainly a lipid spectrum, should show changes that could be assigned to the additional molecular species mentioned.…”

Vision enhancement system for detection of oral cavity neoplasia based on autofluorescence

“…The possible contributions to the optical signal from metabolic cofactors NADH and FAD, collagen cross-links, and hemoglobin might be affected when tissue is resected, and the optimal activation wavelengths in vivo might differ from those determined on excised tissue. Schomaker et al 30 have demonstrated that NADH present in the tissue is oxidized to NAD + in anaerobic conditions initiated by tissue excision, and fluorescence from this metabolic cofactor decreases exponentially within 2 hours after the resection. To minimize this effect, we imaged the tissue immediately after excision, with the maximum time elapsed not exceeding 1 hour, minimally affecting tissue viability.…”

Autofluorescence spectroscopy for the diagnosis of cervical intraepithelial neoplasia

“…Autofluorescence has been used to distinguish adenomatous polyps and normal colon 8 . Other sites for autofluorescence detection are, for example, the urinary bladder and the bronchus 9,10 .…”