Evaluation of water equivalency of Plastic WaterTM for high-energy electron beams using IAEA TRS-398 Code of Practice

Introduction. In the International Code of Practice for dosimetry TRS-398 published by International Atomic Energy Agency (IAEA), water is recommended as the reference medium for the determination of absorbed dose for high-energy electron beams. Plastic phantoms may be used under certain circumstances for electron beam dosimetry for beam qualities R50 < 4g/cm2 (E0 below 10 MeV). In our study, water equivalency of Plastic WaterTM was evaluated in order to determine fluence scaling factors hpl for Plastic Water. Extended set of measurements in water and in Plastic Water were performed. Material and methods. The absorbed dose was determined according to IAEA TRS-398 dosimetry protocol following recommendations for all relevant parameters involved. Water equivalency of Plastic Water was evaluated for five electron beams with nominal energies from 6 MeV to 18 MeV generated by linear accelerator Varian Clinac 2100 C/D. Adequate dosimetry equipment was used throughout the measurements and reference conditions, set by IAEA TRS-398, were followed carefully. Results. The results are presented as ratios Dpl /Dw of absorbed dose in Plastic Water and water. Upon the selection of electron energy, the ratios vary from 0.9990 1.0058 with combined uncertainties (1SD) of 0.46% 0.68%. From the measured data, the fluence scaling factors hpl were determined and found to be in the range from 0.9942 to 1.0010. Measurements were taken over a period of 18 months, within the frame of a Coordinated Research Project of the International Atomic Energy Agency. Conclusions. Our results are compatible with previously published data.