The Pedra Technologies' PedraTM device is a non-invasive, diagnostic device intended to measure foot perfusion by assessing blood flow. The PedraTM device comprises a compact instrument console connected to a sensor that is pasted onto the patient's foot during perfusion assessment. Through skin contact, the device is able to monitor tissue perfusion at depths of up to 7.5mm. The monitor console contains opto-electronic instrumentation including coherent infrared light sources, photo detectors, and display/control electronics. The sensor comprises passive fiber-optic conduits, which transfer infrared light from the console to the patient, and relays scattered light from the patient back to the console. The intensity of light emitted from the sensor is less than 3 mW, well within the safety envelope of Class I laser systems and comparable (or lower than) other commercially available devices such as laser Doppler systems. The sole point of contact with the patient is a layer of medical grade adhesive tape, which is used to paste the flat sensor onto intact skin.

General Inclusion Criteria:

1. The patient is a male or non-pregnant female ≥ 40 to 90 years of age
2. The patient is willing to comply with protocol-specified follow-up evaluations
3. The patient has been informed of the nature of the study, agrees to its provisions and has willingly provided written informed consent, approved by the appropriate Ethics Committee (EC)

Cohort Specific Inclusion Criteria:

Critical Limb Ischaemia Group Inclusion Criteria:

1. The subject is referred for a percutaneous peripheral revascularisation procedure on one of their lower limbs within 2 weeks of Baseline assessments.
2. Rutherford grade 4 or 5 critically ischemic foot, where the primary intention is to treat at least one occluded tibial vessel or 2 severely stenosed tibial vessels.

Peripheral Arterial Disease Group Inclusion Criteria:

1. The subject is referred for a percutaneous peripheral revascularisation procedure on one of their lower limbs within 2 weeks of Baseline assessments.
2. This subject must have a clinical diagnosis of claudication and duplex or CT-confirmed SFA or popliteal artery stenoses greater than 70%, with no intention of primarily treating any tibial disease at this encounter.

PAD-Free Group Inclusion Criteria:

1. The subject is recruited voluntarily
2. Absence of peripheral vascular disease determined by questionnaire and clinical review (triphasic signals on hand-held Doppler)

Exclusion Criteria:

1. Infusion of vasoactive medications within the past 24 hours
2. The presence of a known chronic history of anaemia (i.e. Hb <8g/dL)
3. Congestive heart failure defined by NYHA Classification 3 or 4
4. The absence of intact skin at suitable measurement sites on the foot.
5. The presence of invasive soft tissue infection in the toes spreading into the forefoot.
6. The presence of physical impediment to the method of measurements being completed (i.e. absent first two toes, extensive ulceration, excessive oedema, pressure dressings or heavy bandaging, etc.)
7. The presence of a non-salvageable foot or a Rutherford 6 wound.
8. The presence of other conditions, which in the opinion of the Investigator, may compromise the subject safety or comfort.
9. The presence of other conditions, which in the opinion of the Investigator, may compromise the accuracy of the data obtained.
10. The patient is a vulnerable or protected adult, or is unable to provide consent.
11. The patient is unable to comply with the measurement protocol.
12. Pregnant subjects

The 3 distinct subjects groups are divided as such:

• Critical Limb Ischaemia (CLI) Group with tibial arterial disease: Up to 20, but at least 8 subjects with a Rutherford grade 4 or 5 critically ischemic foot, where the primary intention is to treat at least one occluded tibial vessel or 2 severely stenosed tibial vessels. The treatment of SFA stenoses of less than 70%, as confirmed by duplex or CT, is acceptable in parallel in this group.
• Peripheral Artery Disease (PAD) Group with SFA disease: Up to 20, but at least 8 subjects with a clinical diagnosis of claudication and duplex or CT-confirmed SFA stenoses greater than 70%, with no intention of primarily treating any tibial disease at this encounter.
• PAD-free Group (Healthy Volunteer Group): Up to 20 subjects with no clinical diagnosis of peripheral vascular disease.