Non‐invasive, dynamic imaging of murine intestinal motility

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Abstract
Background After intravenous (i.v.) administration, indocyanine green (ICG) is known to be secreted into bile from the liver via the biliary tracts, enabling fluorescent delineation of the intestine. In addition, ICG is a near-infrared (NIR) excitable fluorophore, capable of providing exogenous contrast for rapid NIR fluorescence imaging. We sought to quantify the intestinal motility using dynamic NIR fluorescence imaging after injection of ICG. Methods C57BL6 mice were dynamically imaged immediately before and up to 24 h after i.v. and intradermal (i.d.) injection of 50 and 10 μL of ICG, respectively. Necropsy was also performed 1 h postinjection and the entire gastrointestinal tract was isolated and exposed for ex vivo fluorescence imaging. Key Results The secretion of ICG-laden fluorescent bile into the duodenum was observed in vivo and confirmed in situ. Different patterns of the intestinal motility, such as peristaltic and segmental motions, were dynamically imaged in vivo. Our imaging data showed that the frequency of contractions ranged from 27 to 35 cycles min−1 and the propagation velocity of peristaltic waves ranged from 0.82 ± 0.5 to 2.04 ± 1.12 cm s−1. Conclusions & Inferences Dynamic NIR fluorescence imaging with injection of ICG can provide a method for diagnostic motility testing for intestinal motility disorders or dysfunction and for potential evaluation of therapeutic agents.