This study is designed to evaluate the ability of Spatial Frequency Domain Imaging (SFDI) to measure perfusion in lower extremities and to understand how it might be used in a podiatry clinic. SFDI is a non-contact optical imaging technology that measures tissue functional (blood volume, tissue oxygen saturation) and structural information (scattering index) across a large field of view. Our hypothesis is that SFDI parameters can eventually become a quantitative tool to assess foot health and identify patients at risk for ulcer formation. This phase of the study is designed to correlate SFDI outputs to current clinical risk categories