A bias current detecting means for outputting an electric signal corresponding to the current flowing through the bias line, and detecting means with an electrical signal, a comparator for outputting a result of comparison between the comparison voltage value at which the differential means has a differential electric signal the integrated value comparing means for outputting a result it is determined that an integrating means for a period integrating a predetermined value, the value integrating means is integral exceeds a predetermined threshold, exposure of radiation to whether or not started anda determining exposure start determining means, exposure start determination means, the exposure of the radiation on the basis that one output is changed at least one of the integrated value comparing means or the output of the comparator is in standby mode radiographic imaging apparatus is characterized in that to determine that it has been started.バイアス線を流れる電流に応じた電気信号を出力するバイアス電流検出手段と、電気信号を微分する微分手段と、微分手段が微分した値を比較電圧と比較した結果を出力する比較器と、電気信号の値を所定の期間積分する積分手段と、積分手段が積分した値が所定の閾値を越えたことを判定し結果を出力する積分値比較手段と、放射線の曝射が開始されたか否かを判定する曝射開始判定手段と、を有し、曝射開始判定手段は、待機モードでは比較器の出力または積分値比較手段のうち少なくとも一方の出力が変化したことに基づいて放射線の曝射が開始されたことを判定することを特徴とする放射線画像撮影装置。
