Feasibility study of glass dosimeter postal dosimetry audit of high-energy radiotherapy photon beams

Introduction: The characteristics of a glass dosimeter were investigated for its potential use as a tool for postal dose audits. Reproducibility, energy dependence, field size and depth dependence were compared to those of a thermoluminescence dosimeter (TLD), which has been the major tool for postal dose audits worldwide. Materials and methods: A glass dosimeter, GD-302M (Asahi Techno Glass Co.) and a TLD, TLD-100 chip (Harshaw Co.) were irradiated with gamma-rays from a Co-60 unit and X-rays from a medical linear accelerator (4, 6, 10 and 20 MV). Results: The dosimetric characteristics of the glass dosimeter were almost equivalent to those of the TLD, in terms of utility for dosimetry under the reference condition, which is a 10 X 10 cm(2) field and 10 cm depth. Because of its reduced fading, compared to the TLD, and easy quality control with the ID number, the glass dosimeter proved to be a suitable tool for postal dose audits. Then, we conducted postal dose surveys of over 100 facilities and got good agreement, with a standard deviation of about 1.3%. Conclusions: Based on this study, postal dose audits throughout Japan will be carried out using a glass dosimeter. (c) 2007 Elsevier Ireland Ltd. All rights reserved.