1 Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, UK.
2 Biomedical Physics, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, UK.
3 School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.
4 Department of Radiology, Massachusetts General Hospital, Athinoula A Martinos Center for Biomedical Imaging, Boston, MA, USA.
5 Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA. adrienne.campbell@nih.gov.