Dynamic multispectral NIR/SWIR for lymphovascular architectural and functional quantification.

SIGNIFICANCE

Although the lymphatic system is the second largest circulatory system in the body, there are limited techniques available for characterizing lymphatic vessel function. We report shortwave-infrared (SWIR) imaging for minimally invasive quantification of lymphatic circulation with superior contrast and resolution compared with near-infrared first window imaging.

AIM

We aim to study the lymphatic structure and function via SWIR fluorescence imaging.

APPROACH

We evaluated subsurface lymphatic circulation in healthy, adult immunocompromised salt-sensitive Sprague-Dawley rats using two fluorescence imaging modalities: near-infrared first window (NIR-I, 700 to 900 nm) and SWIR (900 to 1800 nm) imaging. We also compared two fluorescent imaging probes: indocyanine green (ICG) and silver sulfide quantum dots (QDs) as SWIR lymphatic contrast agents following intradermal footpad delivery in these rats.

RESULTS

SWIR imaging exhibits reduced scattering and autofluorescence background relative to NIR-I imaging. SWIR imaging with ICG provides 1.7 times better resolution and sensitivity than NIR-I, and SWIR imaging with QDs provides nearly two times better resolution and sensitivity with enhanced vessel distinguishability. SWIR images thus provide a more accurate estimation of vessel size than conventional NIR-I images.

CONCLUSIONS

SWIR imaging of silver sulfide QDs into the intradermal footpad injection provides superior image resolution compared with conventional imaging techniques using NIR-I imaging with ICG dye.