1. Metrology for Medical Physics Centre, National Physical Laboratory, Teddington, UK
2. Division of Medical Physics, Erasmus MC Cancer Institute, Rotterdam, The Netherlands
3. Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel (VUB), Brussels, Belgium
4. Radiotherapy Department, Iridium Kankernetwerk, Antwerp, Belgium
5. Department of Medical Physics, Royal Surrey County Hospital NHS Foundation Trust, Guildford, UK
6. Department of Physics, University of Surrey, Guildford, UK