1. 2nd Department of Radiology, Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece
2. Medical Physics Program, University of Massachusetts Lowell, 265 Riverside St, Lowell, MA 01854, USA
3. School of Health Sciences, Medical School, National and Kapodistrian University of Athens, 75 Mikras Assias Street, 11527 Athens, Greece
4. Laboratory of Biology, Department of Basic Medical Sciences, Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece
5. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece