Gary Leeming1, John Ainsworth1, David A Clifton2. 1. Centre for Health Informatics, Division of Informatics, Imaging and Data Science, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK. 2. Department of Engineering Science, University of Oxford, Oxford OX3 7DQ, UK. Electronic address: davidc@robots.ox.ac.uk.