1 Centre for Medical Image Computing and Dept of Computer Science, University College London, London, UK. Electronic address: marco.palombo@ucl.ac.uk.
2 Centre for Medical Image Computing and Dept of Computer Science, University College London, London, UK; Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal.
3 Centre for Medical Image Computing and Dept of Computer Science, University College London, London, UK.
4 Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal.