4. Presence of significant stenosis but not occlusion of femoropopliteal arteries including the common femoral artery, superficial femoral artery and popliteal artery as determined by: Duplex ultrasound imaging OR lower extremity computed Tomography Angiography (CTA) OR lower extremity magnetic resonance angiography (MRA) OR lower extremity catheter-based contrast arteriography. Each of these noninvasive and invasive anatomic assessments will identify patients with at least a 50% stenosis in the affected segment