Performance Improvement of Lead(Ⅱ)Iodide Dosimeter by Addition of Gadolinium Oxysulfide Powder and Applicability to Radiotherapy Quality Assurance Evaluation

摘要

In radiotherapy, quality assurance (QA) procedures to verify the safety of treatment are considered to be critically important. However, owing to general problems associated with dosimeters, active research has been conducted to replace them. Herein, we intended to maximize the sensitivity of PbI2 on radiation by the visible light emitted from the phosphor. For this purpose, the PbI2 based pure and hybrid sensors containing Gd2O2S:Tb (0-3 wt%), a phosphor with excellent fluorescence efficiency, were fabricated. The sensors were irradiated with photons of 6 MV and 15 MV, and the reaction characteristics were compared and evaluated. Reproducibility evaluation results showed that the criterion of RSD 1.5% was not met in any of the cases except for the pure PbI2 sensor. In the linearity evaluation, all sensors showed excellent reliability (R-2 = 0.9999). For sensitivity evaluation, the 1 wt% sensor showed values that were 1.88 times and 1.75 times better, respectively for each energy than those of the pure PbI2 sensor, indicating superior performance. The 2 wt% and 3 wt% sensors also showed sensitivity values exceeding 1.13 times that of pure PbI2 sensor, although these values were lower than those of the 1 wt% sensor. None of the sensors showed any significant difference from the pure PbI2 sensor for dose rate dependence and percentage depth dose evaluation.