Photodynamic diagnosis with 5-aminolevulinic acid for intramucosal cancer using green light

摘要

Photodynamic diagnosis (PDD) of gastric cancer with protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA)will lead to a method to estimate the invasive depth. The excitation light for ALA-based PDD is attenuated by absorptionand scattering of the mucosal tissue according to its wavelength and the difference contains the fluorophore depthinformation. To realize the method to estimate the invasive depth for the intramucosal cancer, this study investigated thedifferences of the attenuation rate between two excitation wavelengths. Considering the optical properties of mucosa andPpIX, relationships between the invasive depths of cancer containing PpIX and the fluorescence intensity ratios detectedfrom the mucosa were estimated using a numerical model. An experiment was also performed using a pellet made of epoxyresin containing PpIX. The excitation lights with wavelengths of 405 and 505 nm having the same power density wereeach used to irradiate the pellet placed at the fluorophore depth of 0 mm, 1.0 mm, and 1.7 mm from the mucosal surfaceto obtain fluorescence images, and the average fluorescence intensities of the images were evaluated. The numerical andexperimental results suggested the possibility to estimate the fluorophore depth of the PpIX fluorescence source bycomparing the fluorescence images with excitation lights at wavelengths of 405 and 505 nm.