1. Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
2. Institute for Condensed Matter Physics, Technische Universit¨at Darmstadt, Darmstadt, Germany
3. Computer Science Department and Center for Artificial Intelligence, Technische Hochschule Nürnberg Georg Simon Ohm, Nuremberg, Germany
4. Nature Inspired Computing and Engineering Research Group, Computer Science Research Centre, University of Surrey, Guildford, UK
5. Department of Medical Physics and Biomedical Engineering, University College London, London, UK
6. Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus