The radioluminescence was measured using a fluorescence spectrophotometer (Omniλ 300i, Zolix). For X-ray imaging measurement, a tungsten anode X-ray tube (Hamamatsu Photonics, L11831-01) was used as the X-ray source. The X-ray tube voltage was adjusted from 40 kV to 90 kV, and the current was adjusted from 10 µA to 200 µA to change the dose rate of the X-rays. The dose rate of X-rays was further finemodulated by changing the distance between the SC scintillator and the X-ray source.