1. Department for Dosimetry and Quality of Radiological Procedures Institute of Oncology Ljubljana Zaloška 2 1000 Ljubljana Slovenia
2. Medical Physics Service North Estonia Medical Centre J. Sütiste tee 19 13419 Tallinn Estonia
3. Medical Physics Department University Hospital Rijeka Krešimirova 42 51000 Rijeka Croatia
4. Department of Radiation Oncology University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center Pittsburgh PA USA