Department of Medical Physics, School of Medicine, University of Patras, 26500 Patras, Greece. severina@heart.med.upatras.gr|Department of Medical Physics, School of Medicine, University of Patras, 26500 Patras, Greece. severina@heart.med.upatras.gr|Department of Medical Physics, School of Medicine, University of Patras, 26500 Patras, Greece. severina@heart.med.upatras.gr