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

BackgroundThe 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.ObjectiveTo 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.DesignCross-sectional study.Patients and InterventionsA 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 (F365ex) and 405 nm (F405ex) on cross sections of the samples, ratio images were created by dividing F365ex by F405ex. The excitation-emission wavelength combinations in F365ex and F405ex were optimized for NADH fluorescence and reference fluorescence.Main Outcome MeasurementsThe F365ex/F405ex ratio in the tumorous (T) and normal (N) mucosa.ResultsF365ex/F405ex 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 F365ex/F405ex ratio images for tubular adenomas was significantly higher than that for hyperplastic polyps. The signal intensity in F365ex/F405ex 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 F365ex/F405ex ratio images.LimitationsEx vivo experiment.ConclusionsThese 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.