Computed tomography for in vivo deep over-1000 nm near-infrared fluorescence imaging

This study aims to develop a novel cross-sectional imaging of fluorescence in over-1000 nm near-infrared (OTN-NIR), which allows in vivo deep imaging, using computed tomography (CT) system. Cylindrical specimens of composite of OTN-NIR fluorophore, NaGdF₄ co-doped with Yb³⁺ and Ho³⁺ (ex: 980 nm, em: 1150 nm), were embedded in cubic agar (10.5-12 mm) or in the peritoneal cavity of mice and placed on a rotatable stage. When the fluorescence from inside of the samples was serially captured from multiple angles, the images were disrupted by the reflection and refraction of emitted light on the sample-air interface. Immersing the sample into water filled in a rectangular bath suppressed the disruption at the interface and successfully reconstructed the position and concentration of OTN-NIR fluorophores on the cross-sectional images using a CT technique. This is promising as a novel three-dimensional imaging technique for OTN-NIR fluorescent image projections of small animals captured from multiple angles.