Investigation of the dosimetric characteristics of radiophotoluminescent glass dosimeter for high-energy photon beams

The aim of this work was to investigate the dosimetric characteristics of radiophotoluminescent glass dosimeter (RPLGD) for high energy photon beams in both flattening filter mode and flattening filter free (FFF) mode. The dosimetric characteristics of RPLGD model GD-302M were studied in 6 MV photon beams for the reproducibility of dosimeter reader, uniformity and reproducibility of RPLGD, dose linearity (range from 1 to 20 Gy), repetition rate, and angular dependence. In addition, the energy responses were observed in flattening filter mode (6 MV, 10 MV, and 15 MV) from Varian Clinac C-series and FFF mode (6 MV_FFF and 10 MV_FFF) from Varian TrueBEAM system. The FGD-1000 reader system exhibited stable readout. The entire number of 100 RPLGDs showed good uniformity and reproducibility within ±1.5%. Furthermore, the signal from RPLGD demonstrated a linear proportion to the radiation dose (r = 0.999), and no energy dependence was observed. For repetition rate response of flattening filter mode and FFF mode, the maximum error of relative response to 400 MU/min were 0.977±0.006 and 0.986±0.017, respectively. The response of RPLGD reached 1.00 at ±30° gantry angle while at +90° gantry angle, the RPLGD response was 8% lower compared to -90° gantry angle because the attenuation effect was more pronounced. We conclude that the RPLGD is capable to measure radiation dose since it provides desirable dosimetric properties such as good uniformity and reproducibility of RPLGD including the reader system. Besides, RPLGD is available with small active readout area which adds benefit for clinical implementation in radiotherapy, especially for advanced techniques.