Peripheral Arterial Disease is the narrowing and blocking of the blood vessels that supply the legs and feet. It is a common and progressive condition that affects patients of all backgrounds and genders and is more common in people with other problems such as heart disease, high blood pressure and diabetes mellitus as well being linked to ageing. It can be a severe disease and in 20% of patients can lead to pain on walking short distances and 2% of people can lead to painful ulceration, constant pain and can lead to amputation of part or all of the affected leg. The investigators are researching 2 different types of new scanning techniques to measure the amount of blood that is circulating within the tissues of the leg and foot (known as tissue perfusion). The investigators want to measure tissue perfusion in people both with and without Peripheral Arterial Disease. This will help find a more sensitive method to diagnose Peripheral Arterial Disease earlier and help identify those with worsening arterial narrowing before they develop ulcers. Measuring tissue perfusion will guide doctors with decision about what procedure can be performed to improve blood flow in people with Peripheral Arterial Disease . Patients with all degrees of Peripheral Arterial Disease will be eligible to take part in this study. The study will take part at University College London and Royal Free Hospital. The research will run along side normal investigations and treatment for Peripheral Arterial Disease and the study period will be 2 years. Participants will undergo an ultrasound scan of the lower leg with an injection of a special dye into a vein in the arm, as well as a magnetic resonance