1. Institute of Computer Science, Foundation for Research and Technology Hellas (FORTH), GR-700 13 Heraklion, Greece
2. Department of Electrical and Computer Engineering, Hellenic Mediterranean University, GR-710 04 Heraklion, Greece
3. Laboratory of Optics and Vision, School of Medicine, University of Crete, GR-710 03 Heraklion, Greece
4. Biomedical Research Institute, Foundation for Research and Technology Hellas (FORTH), GR-451 10 Ioannina, Greece
5. Department of Materials Science and Engineering, Unit of Medical Technology and Intelligent Information Systems, University of Ioannina, GR-451 10 Ioannina, Greece