1. Department of Physics, School of Natural Sciences, University of Patras, Rio, 26504 Patras, Greece
2. Medical Image and Signal Processing Laboratory, Department of Biomedical Engineering, Technological Educational Institute of Athens, Ag. Spyridonos, Egaleo, 12210 Athens, Greece
3. Department of Pathology, University Hospital of Patras, 26504 Rio, Greece
4. Department of Medical Physics, School of Health Sciences, Faculty of Medicine, University of Patras, Rio, 26504 Patras, Greece