An investigation of an infrared ray electronic endoscope with a laser diode light source

An infrared ray electronic video-endoscope with a laser diode light source was used to obtain information on the submucosal area. As contrast medium we employed indocyanine green, which has a light absorption peak in the infrared range. The wavelength of the laser diode was set to 810 nm as suggested by the results of the spectrophotometric study on the reflected light at fingertips after injection of ICG (3 mg/kg). Using this system we inspected the stomach under visible light and then continuously under infrared light before and after intravenous injection of ICG (2 mg/kg). A dendritic figure with fine ramifications emerged in the early stage after intravenous injection of indocyanine green, which was not seen under visible light. These features of the figure visualized by the infrared endoscope suggest that they have a close relationship with blood vessels and blood circulation beneath the mucosal surface. This infrared electronic endoscope system provides submucosal information more readily and at a lower cost than ever before, and also the infrared lighting method of this system could be applied to almost all available electronic endoscopes by modulating infrared cutting filters, so it could become a valuable clinical tool.