Multifunctional in vivo vascular imaging using near-infrared II fluorescence

TL;DR

This paper demonstrates real-time, high-resolution in vivo vascular imaging in mice using NIR-II fluorescence with single-walled carbon nanotubes, enabling detailed visualization and blood flow quantification beyond traditional methods.

Contribution

The study introduces a novel NIR-II fluorescence imaging technique with superior spatial and temporal resolution for deep tissue vascular imaging in vivo.

Findings

Achieved ~30 microns spatial resolution at 1-3 mm depth

Enabled differentiation of arteries and veins via hemodynamics

Quantified blood velocity beyond ultrasonography capabilities

Abstract

In vivo real-time epifluorescence imaging of mouse hindlimb vasculatures in the second near-infrared region (NIR-II, 1.1~1.4 microns) is performed using single-walled carbon nanotubes (SWNTs) as fluorophores. Both high spatial resolution (~30 microns) and temporal resolution (<200 ms/frame) for small vessel imaging are achieved 1-3 mm deep in the tissue owing to the beneficial NIR-II optical window that affords deep anatomical penetration and low scattering. This spatial resolution is unattainable by traditional NIR imaging (NIR-I, 0.75~0.9 microns) or microscopic computed tomography (micro-CT), while the temporal resolution far exceeds scanning microscopic imaging techniques. Arterial and venous vessels are unambiguously differentiated using a dynamic contrast-enhanced NIR-II imaging technique based on their distinct hemodynamics. Further, the deep tissue penetration, high spatial and temporal resolution of NIR-II imaging allow for precise quantifications of blood velocity in both normal and ischemic femoral arteries, which are beyond the capability of ultrasonography at lower blood velocity.