輝尽性蛍光体プレートを用いて取得したX線画像上の黒点発生の解明に向けたモンテカルロシミュレーション

概要

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Caused by an accident of nuclear power plants at Fukushima in March 2011, many radioisotopes were spread to the environment. In medical front, the black spots were appeared on the radiographic image stored by the phosphor plate and they had a negative impact on the diagnostic imaging. The aim of this study is to simulate the effect of the emitted radiation(β-rays and/or γ-rays)on the luminescence of the photostimulable phosphor, and to evaluate the most effective RI to produce the black spots. We focused attention to the five nuclides(90Sr-90Y, 131I, 134Cs, 137Cs), and contributions for appearance of the black spots were calculated. In the simulation, the β-rays and γ-rays of each nuclide were individually estimated. As a result, we found that the contribution of β-rays was much larger than that of the γ-rays. Moreover, we considered about the main nuclei to produce the black spots based on the simulated results and the measured data by MEXT(Ministry of Education, Culture, Sports, Science and Technology). In the case in which RI was directly adhered on the phosphor plate, the β-ray emitted from 137Cs was main cause. In the other case in which RI was attached at the supporting equipments(cassette etc.), the γ-ray emitted from 134Cs was main cause.