1. Medical Physics Unit, 2nd Department of Radiology, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, 124 62 Athens, Greece
2. Department of Radiation Oncology and Stereotactic Radiosurgery, Mediterraneo Hospital, 166 75 Athens, Greece
3. Radiation Oncology Unit, 1st Department of Radiology, Aretaieion University Hospital, Medical School, National and Kapodistrian University of Athens, 115 28 Athens, Greece
4. Radiation Oncology Unit, 2nd Department of Radiology, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, 124 62 Athens, Greece