1. Institute of Physics, Kazimierz Wielki University, Bydgoszcz , Poland
2. Oncology Center, Medical Physics Department, Bydgoszcz , Poland
3. Chair and Clinic Oncology and Brachytherapy, Nicolaus Copernicus University, Toruń , Poland
4. Institute of Physics, Nicolaus Copernicus University, Toruń , Poland
5. Faculty of Technical Physics, Poznan University of Technology, Piotrowo 3, 60-965 Poznan , Poland