Abstract Body: Critical limb ischemia (CLI) is an advanced stage of peripheral arterial disease and is associated with high rates of limb loss, morbidity, and mortality. CLI is characterized by severe impairment of peripheral tissue perfusion and microvascular dysfunction. Although revascularization is the primary therapeutic technique for restoring vascular patency, clinical outcomes of the procedure remain variable. Existing modalities provide limited insight into immediate restoration of perfusion in distal extremities (such as feet) and microcirculatory function post- revascularization. Our prior work focused on developing a bedside near infrared spectroscopy (NIRS)-based imaging approach to monitor spatial hemodynamic changes in real-time to assess tissue perfusion at distal extremities. The objective of this study is to apply our innovative spatio-temporal NIRS imaging approach to assess the extent of improvement in tissue perfusion in response to revascularization in subjects with CLI. In this study, images of foot were acquired longitudinally from CLI patients(n=10) pre- and post-lower-extremity revascularization and healthy controls(n=10) using leg elevation maneuver to assess hemodynamic changes. Hemodynamic responses were normalized to an initial timepoint, and perfusion change rates between the resting and reperfusion phases were determined. From our preliminary analysis, we observed that the resting state for both the control and CLI individuals(n=1) demonstrated a steady baseline within 1% of this initial value. Following leg elevation and lowering for reperfusion, the hemodynamic signals from control subject(n=1) increased by 7% over the course of 1 minute, demonstrating restoration of peripheral tissue oxygenation after the leg was lowered. Prior to reperfusion, these hemodynamic signals for CLI patient remained close to the baseline, indicating impaired blood flow to the foot. Following the revascularization procedure, normal rates of reperfusion were restored in the same CLI subject as indicated by a 5% increase in the hemodynamic signal after leg elevation stimulus. Ongoing work focuses on assessing the extent of improved perfusion in response to the revascularization procedure across all recruited subjects, and its comparison to perfusion observed in control subjects. Future work will use this technique longitudinally across weeks, to monitor hemodynamic changes post-revascularization procedures in CLI subjects and assess their clinical outcomes.