Reflected illumination-type imaging system for the development of infrared fluorescence endoscopy

: Fluorescent labeled monoclonal antibodies against carcinoembryonic antigen (CEA) may provide a specific label for lesions of the GI tract. We previously developed an indocyanine green (ICG) derivative (ICG N-hydroxy sulfo succinimide ester; ICG-sulfo-Osu) as a fluorescent label that is excited by infrared rays and is suitable for vital immunohistochemical staining. We also previously developed a transmitted illumination-type (transmitted type) fluorescence imaging system that uses infrared rays to detect ICG-sulfo-Osu. In this paper we describe a new reflected illumination-type (reflected type) imaging system for infrared fluorescence endoscopy. We tested the efficacy of this system on sections of human esophagus and normal skeletal muscle stained with ICG-sulfo-Osu labeled anti-epithelial membrane antigen (EMA) antibody, and on sections of human gastric cancer tissue stained with ICG-sulfo-Osu labeled anti-CEA antibody. Infrared fluorescent images were obtained with both fluorescent antibodies, and results correlated well with oxidized DAB-positive sites. Vital immunohistochemical staining of micro cancers should be detectable by exciting an ICG-sulfo-Osu labeled antibody specific to the tumor cells with infrared rays, using this reflected type imaging system.