In gastrointestinal endoscopic surgery, bleeding from the accidental resection of hidden vessels is a major complication, requiring immediate conversion to open surgery. Methods of visualizing occult vessels have been proposed using the FDA approved fluorescent dye Indocyanine green (ICG), but Native label-free fluorescence of the submucosa—present up till about 886 nm—prevents the use ICG in near-infrared (NIR) window I (700 nm to 900 nm). Instead, absorption imaging is preferred; the darker vessels are visible to 4.5 mm deep. Using data from Raman scattering, absorption, native fluorescence, SHG and the photon excitation fluorescence we investigate the spectral properties and propose optimal parameters for differentiation of blood vessels from surrounding tissue in a variety of tissue types in NIR window II (1000 nm to 1350 nm) and NIR window III (1550 nm to 1900 nm, the “Golden Window”) as a complement to absorption imaging.
Injuries to main vascular structures within the sub mucosa present a serious complication during surgery. There is no evidence-based treatment to prevent this type of injury, so detection is critical. Using a combination of absorption and fluorescence imaging we can detect blood vessel phantoms to a depth of 7 mm in intestinal sub-mucosa. Using an illumination source at 850, and reading the cross-polarized reflected signal also at 850 gives the absorption image. Simultaneous excitation of ICG at 785 nm creates a fluorescent response that is used for contrast enhancement.