[1] Univ Edinburgh, Dept Publ Hlth Sci, Wolfson Unit Prevent Peripheral Vasc Dis, Edinburgh EH8 9AG, Midlothian, Scotland
[2] Royal Infirm Edinburgh, Dept Med Radiol, Edinburgh, Midlothian, Scotland
[3] Royal Infirm Edinburgh, Dept Surg, Edinburgh, Midlothian, Scotland