The goal of the study is to identify and validate flow measurement and ultrasound images in patients undergoing vein bypass surgery below-knee and above ankle

Inclusion Criteria:

• Chronic Limb-Threatening Ischemia as defined by presence of Peripheral Artery Disease (PAD) in combination with rest pain, gangrene, or a lower limb ulceration>2 weeks duration (ref Global Guidelines)
• Atherosclerotic infra-popliteal PAD
• Adequate distal anastomotic target (crural, tibial or popliteal below the knee with one single run-off) between knee and ankle distal to the stenotic/occluded segment.
• Available autogenous vein conduit based on preoperative vein mapping.
• Understand the nature of the procedure and willingness to comply with protocol. Attend follow-up appointments and provide written informed consent.

Exclusion Criteria:

• Bypass with artificial conduit or cryopreserved allografts
• Bypass for non-atherosclerotic lesions
• Life-expectancy less than 2 years
• Any psychological, developmental, physical or emotional disorder that the investigator believes would interfere with surgery or follow-up.
• Any condition that the investigator believes should exclude participation.
• Excessive risk for adverse events during open surgery as judged by the investigator.

Chronic Limb-Threatening Ischemia patients scheduled to undergo a vein bypass with or without arterial inflow reconstruction to a below-knee and above ankle target