Autofluorescence imaging to optimize 5-ALA-induced fluorescence endoscopy of bladder carcinoma

To design an optical system for detecting autofluorescence (AF) of bladder tumors and to determine the success of reducing the false-positive rate of 5-aminolevulinic acid-induced fluorescence endoscopy (AFE). AFE provides significantly higher sensitivity in detecting and localizing bladder carcinoma compared with white light endoscopy. The specificity of AFE is equivalent to white light endoscopy, mostly because of the false-positive fluorescence of chronic cystitis lesions. Laser-induced spectral autofluorescence detection is also an efficient method in the diagnosis of bladder carcinoma.

Bladder tissue was excited to AF using the D-Light (375 to 440 nm) after regular AFE with detection of fluorescence-positive areas. The optical image was produced using a special RGB camera. Biopsies were taken from AFE-positive areas, the peritumoral edges, and normal bladder mucosa. The AF images of the suspicious areas were compared with the AFE images and the histologic results.

A total of 43 biopsies were histologically examined (24 benign and 19 neoplastic). AF imaging showed contrast differences between papillary tumors, flat lesions, and normal mucosa. The combination of AFE with AF raised the specificity of AFE alone from 67% to 88%.

AF imaging is possible. The value of the method in reducing the false-positive rate of the highly sensitive AFE needs to be validated with higher numbers. The combination of AF with AFE had a 20% higher specificity than AFE alone in our study.