Investigation of the Excitation Wavelength for Extension of Diagnostic Depth in 5-aminolevulinic Acid-based Photodynamic Diagnosis of Bladder Cancer

Extension of diagnostic depth in 5-aminolevulinic acid-based photodynamic diagnosis (ALA-PDD) for bladder cancer was investigated by selecting the wavelength of the excitation light. Numerical calculation based on the light attenuation in bladder tissue and the absorption coefficient of PpIX showed that the fluorescence intensity with the green excitation light of 505 nm wavelength was highest for a tumor located at a depth of 0.9 mm or deeper. The diagnostic depth in an extracted porcine bladder tissue using an excitation wavelength of 505 nm was compared with that using the blue-violet excitation light of 405 nm wavelength that is currently used in PDD. The fluorescence intensity at the excitation wavelength of 505 nm was higher for a tumor located at a depth of 0.8 mm or deeper. These results indicate that an extension of the diagnostic depth is achieved with the excitation wavelength of 505 nm.