A novel diagnostic method for evaluation of vascular lesions in the digestive tract using infrared fluorescence...

We have developed an infrared fluorescence endoscope to evaluate gastrointestinal vascular lesions. Infrared endoscopy (IRE) after intravenous administration of indocyanine green (ICG) is used at present to examine vascular lesions such as esophageal varices. However, no previous study has compared the sensitivity of infrared fluorescence endoscopy (IRFE) with that of IRE. In this study, we compared the usefulness of IRFE and IRE.

For IRFE we used an infrared endoscope equipped with excitation and barrier filters and an intensified charge-coupled device camera. In preliminary experiments, the observable tissue depth was assessed by wrapping increasing numbers of layers of commercially available pork around a syringe containing a uniform concentration of ICG or by changing the concentration of ICG in a syringe covered by a piece of pork of uniform thickness. In the clinical part of the study, ICG was administered intravenously at different concentrations to patients with esophageal varices and the resulting infrared fluorescent images were evaluated.

The preliminary experiments revealed that the depth of tissue that could be visualized was significantly greater in IRFE than it was in IRE (11.2 mm in IRFE vs. approximately 3.2 mm in IRE). Clear infrared fluorescence was obtained by IRFE at lower concentrations of ICG than the concentrations required to obtain clear images using IRE. In the clinical part of the study, clear infrared fluorescence was observed in a region where esophageal varices had been detected by conventional endoscopy when ICG was administered in doses of 0.005 mg/kg to 0.01 mg/kg, which was lower than the doses used in IRE.

Compared with conventional IRE, IRFE facilitated the observation of deeper layers, and esophageal varices were observed by IRFE following the intravenous administration of a markedly reduced dose of ICG. IRFE, in combining the characteristics of reflected infrared light and fluorescence, may be a useful novel procedure in the diagnosis of vascular lesions in the gastrointestinal tract.