2016 年 33 巻 2 号 p. 32-37
For Quality Assurance of clinical radiation therapy, it is necessary to accurately measure multiple doses, and evaluate and compare the results to the radiation treatment system. Based on the measurements using multiple dosimeters,there is no uncertainty estimation of the delivered dose for accurate analysis. In this study, we focused attention on smalltype optically stimulated luminescence（OSL）dosimeters, and clarified the relationship of uncertainties between the experimental variance associated with multiple data points and the variance predicted by Poisson distribution. The experiments were carried out as follows : fifteen dosimeters were placed in a water equivalent phantom, they were irradiated with X-rays having an acceleration voltage of 10-MV with 167.2 cGy（200 MU）and 2,090 cGy（2,500 MU）. Each dosimeter was read ten times and the experimental variance and predicted variance were analyzed. As a result, we found that the experimental uncertainties were 3.9 and 6.2 times higher than predicted uncertainty when irradiated at 167.2 cGy and 2,090 cGy, respectively. We discuss the relationship of measurement uncertainties. Then, we concluded that the uncertainty of OSL dosimeters was found to be 3%. We also conclude that the OSL dosimeter can be used to measure the absorbed dose in the radiation therapy region.
