Short-wave infrared spatial frequency domain imaging for non-invasive quantification of tissue water content

Spatial frequency domain imaging (SFDI) is a non-invasive technique that can quantify tissue chromophore concentrations. SFDI has been implemented previously using visible and near-infrared wavelengths to provide information on oxy-and deoxy-hemoglobin concentrations for applications including assessment of burn wounds, pressure ulcers, and tumor resections. Further tissue characterization can potentially be achieved using short-wave infrared (SWIR) wavelengths (approx. 1,000-1,700 nm) due to the distinctive absorption bands of water, lipid, and collagen in this spectral range. Quantification of these tissue components may have clinical significance in relation to such topics as inflammation, obesity, and wound healing. Previous work on extending SFDI into the SWIR region combined VIS/NIR-SFDI with planar imaging at SWIR wavelengths1. There is currently no literature that directly performs SFDI in the SWIR range for the absolute quantification of water content. In this study, we used laser sources centered at 980 nm and 1,550 nm to directly perform SFDI at these SWIR wavelengths to capture differences in hydration in a biomedically significant context.