1. Research Associate Division of Engineering, King's College London, Strand, London WC2R 2LS, UK e-mail:
2. Professor Division of Imaging Sciences and Biomedical Engineering, King's College London, St. Thomas's Hospital, London SE1 7EH, UK e-mail:
3. Professor Division of Engineering, King's College London, Strand, London WC2R 2LS, UK; Khalifa University of Science, Technology and Research, P.O. Box 127788, Abu Dhabi, United Arab Emirates e-mail: ;
4. Professor Department of Informatics, King's College London, Strand, London WC2R 2LS, UK e-mail: