INDOCYANINE GREEN (ICG) FLUORESCENCE DETECTION FROM COLON TISSUE USING FLEXIBLE BUNDLE-FIBER OPTICS

Near-Infrared (NIR) imaging of the fluorophore Indocyanine Green (ICG) is only provided clinically via rigid surgical scopes. NIR-ICG using Artificial Intelligence Methods (AIM) has been demonstrated for the real-time classification of rectal cancer [1], but more proximal intestinal applications need a capable flexible NIR endoscope, which is challenging due to the weak quantum yield of ICG and bidirectional energy attenuation over distance. We developed a 2m long, 6.4mm diameter flexible Y-bundled fiberoptic prototype that transmits excitation light (785nm) via a single fiber and collects emitted ICG fluorescence (800-850nm) via multimode fibers. Emission signals from an ICG with Dimethyl sulfoxide (DMSO) solution (7.5 mu M) excited by an 60mW source and isolated using an 840nm bandpass filter were detectable, with significant signal noise from both sample and bundle tip lens reflections needing further refinement. ICG with Bovine Serum Albumin (BSA) depots in bovine-colon mimicking colorectal polyps exhibited reduced reflection while optimizing ICG concentration (determined empirically by comparing fluorescence intensities of incremental concentrations versus surgical use recommendation (4.6 mu M) augmented emission signal strength. Additionally, a long-pass filter (800nm) at the collection tip further cleaned reflections, although the distal excitation lens performance needs further design consideration. Source power intensity, NIR-exposure time and tip-target distance were also proven significant parameters with likely considerable clinical relevance. Initial development of a novel flexible NIR imaging device capable of carrying raw NIR energy for AIM algorithmic calculations has proven feasible although challenges remain regarding signal cleaning/augmentation as well as computerized image construction.