1. Medical Image and Signal Processing Laboratory; Department of Biomedical Engineering, Technological Educational Institute of Athens; 12210 Egaleo Athens Greece
2. Department of Medical Physics; University of Patras; 26504 Rio Patras Greece
3. School of Engineering and Design; Brunel University West London; Uxbridge Middlesex UB8 3PH United Kingdom
4. Department of Pathology; University Hospital of Patras; 26504 Rio Patras Greece