Dose distribution measurement of clinical proton beams with an imaging plate

For an application to the dose-distribution measurement, response of an imaging plate (IP) has been studied with proton beams which are utilized for the radiation therapy. The upper limit of measurable proton dose by the IP system is almost controlled by the readout range of the scanner used. Within this limit, reasonable linear response of an IP to proton dose to water is maintained. Reproducibility of the PSL intensity is fairly good if both the fading characteristics and the lot-dependence of the sensitivity of each IP are taken into account carefully. Stopping power dependence of IP response has been found to be unnegligible for the precise dose evaluation. Following this, in order to examine the resultant radiation damage by proton irradiation, an IP was excessively irradiated by 250 MeV protons. Notable deterioration of PSL signal was found for the fluence more than 5 × 10¹² protons/cm². Next, by using an IP, we have developed a simple and novel method of the 2-dimensional dose-distribution measurement. The effectiveness of this method is demonstrated by a comparison between the measurement and the dose-distribution calculated by a new model.