The effectiveness evaluation of the optically stimulated luminescence for intensity modulated radiation therapy (IMRT)

In this study, we estimated the characteristics of the optically stimulated luminescence dosimeter (OSLD), and confirmed the evaluation of the OSLD for intensity modulated radiation therapy (IMRT) dose verification. For the estimation of the characteristics of the OSLD, reproducibility, dose linearity, energy dependence, dose-rate dependence, and angular dependence were evaluated. To minimize the effect of the reproducibility on the other studies, we selected 17 OSLDs which had the reproducibility variation margin of ±1.5%. The result showed the linearity of the OSLD from 0.5 to 2 Gy, but from 2 to 6 Gy, supra-linearity was observed. The photon-rays and electron-rays energy dependences of the OSLD were ±1% and ±0.9%, respectively. The dose-rate dependences were ±0.4% for photon-rays, ±0.3% for electrons, and the angular dependence was ±0.7%. To estimate the evaluation of the OSLD for IMRT dose verification, 5 IMRT dose verification cases and 5 RapidArc dose verification cases were selected. The correction factors which were measured in the estimation of the characteristics of the OSLD were used in the dose conversion and the IMRT dose verification standard ±5% were increased to ±7%, because of the relatively high combined uncertainty of the OSLD. In this study, we estimate the characteristics of the OSLD in photon-rays and electron-rays, and confirm the evaluation of the OSLD for IMRT dose assessment through the logic flow chart, which concerned the size of the cancer and partiality of the radiation therapy center.