1. Diabetes Research Unit, Royal Hallamshire Hospital, Sheffield, U.K.
2. Academic Unit of Radiology, University of Sheffield, Sheffield, U.K.
3. School of Health, University of Bath, Bath, U.K.
4. Academic Unit of Neurology, University of Sheffield, Sheffield, U.K.
5. Department of Epidemiology and Public Health, Royal Free and University College London Medical School, London, U.K.