Dual-wavelength excitation of mucosal autofluorescence for precise detection of diminutive colonic adenomas

Background: The mucosal layer of the colon contains metabolism-related fluorophores, such as reduced nicotinamide adenine dinucleotide (NADH), which might have the potential to serve as biomarkers for detecting neoplasia. Objective: To examine NADH fluorescence in human colonic adenoma while eliminating the effect of hemoglobin absorption and to develop a novel imaging technique for precise detection of adenomas. Design: Cross-sectional study. Patients and Interventions: A total of 66 endoscopically resected colonic polyps were investigated. After serial acquisition of autofluorescence images between 450 and 490 nm illuminated with dual-wavelength excitation at 365 nm (F-365ex) and 405 nm (F-405ex) on cross sections of the samples, ratio images were created by dividing F-365ex by F-405ex. The excitation-emission wavelength combinations in F-365ex and F-405ex were optimized for NADH fluorescence and reference fluorescence. Main Outcome Measurements: The F-365ex/F-405ex ratio in the tumorous (T) and normal (N) mucosa. Results: F-365ex/F-405ex ratio images showed a 1.81- and 1.12-fold higher signal intensity in the adenomas and hyperplastic polyps, respectively, than in the adjacent normal mucosa. The ratio between signal intensities in tumorous mucosa and normal mucosa in F-365ex/F-405ex ratio images for tubular adenomas was significantly higher than that for hyperplastic polyps. The signal intensity in F-365ex/F-405ex ratio images was not correlated with the hemoglobin concentration index evaluated by reflection images at 550 nm and 610 nm. Diminutive adenomas (<5 mm) and large adenomas were well discriminated in F-365ex/F-405ex ratio images. Limitations: Ex vivo experiment. Conclusions: These results suggest that the precise measurement of NADH fluorescence intensity together with eliminating the influence of blood hemoglobin concentration serves as a method for visualizing colonic adenomas and that the dual-wavelength excitation method is a promising technique applicable to endoscopic detection of early colonic adenomas. (Gastrointest Endosc 2012;75:110-7.)