Dosimetric properties of radiophotoluminescent glass rod detector in high-energy photon beams from a linear accelerator and Cyber-Knife

A fully automatic radiophotoluminescent glass rod dosimeter (GRD) system has recently become commercially available. This article discusses the dosimetric properties of the GRD including uniformity and reproducibility of signal, dose linearity, and energy and directional dependence in high-energy photon beams. In addition, energy response is measured in electron beams. The uniformity and reproducibility of the signal from 50 GRDs using a Co-60 beam are both +/-1.1% (one standard deviation). Good dose linearity of the GRD is maintained for doses ranging from 0.5 to 30 Gy, the lower and upper limits of this study, respectively. The GRD response is found to show little Co-60 beam, 4 MV (TPR1020 = 0.617) and 10 MV energy dependence in photon energies of a 10 (TPR1020 = 0.744) x-ray beams. However, the GRD responses for 9 MeV (mean energy, (E) over bar (z) = 3.6 MeV) and 16 MeV ((E) over bar (z) = 10.4 MeV) electron beams are 4%-5% lower than that for a Co-60 beam in the beam quality dependence. The measured angular dependence of GRD, ranging from 0degrees (along the long axis of GRD) to 120degrees is within 1.5% for a 4 MV x-ray beam. As applications, a linear accelerator-based radiosurgery system and Cyber-Knife output factors are measured by a GRD and compared with those from various detectors including a p-type silicon diode detector, a diamond detector, and an ion chamber. It is found that the GRD is a very useful detector for small field dosimetry, in particular, below 10 mm circular fields. (C) 2004 American Association of Physicists in Medicine.