PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus, capable of decreasing X-ray tube current as desired under consideration of response characteristics in modulation control of X-ray tube current even when rotation speed of an X-ray tube is varied in scanning with the X-ray tube current reduced from a prescribed tube current value when a rotation angle of the X-ray tube is within a prescribed rotation angle range as in X-ray CT scanning to a range including a tissue of high radiation sensitivity.SOLUTION: The X-ray CT apparatus includes a rotation speed setting means 107 to set the rotation speed of the X-ray tube, a rotation angle range setting means 105 to set the rotation angle range &alpha of the X-ray tube of which X-ray tube current is to be reduced from the prescribed tube current value, a relation determining means 108 to determine relation between the rotation angle &theta of the X-ray tube in X-ray CT scanning to an examinee and a tube current value k(&theta) x A(&theta) based on the set rotation speed (cycle) T and the rotation angle range &alpha, and a modulation means 111 to modulate the X-ray tube current in accordance with the determined relation in X-ray CT scanning the examinee.COPYRIGHT: (C)2011,JPO&INPIT【課題】放射線感受性の高い組織を含む範囲をX線CTスキャンするなど、X線管の回転角度が所定の回転角度範囲に属するときにX線管電流を所定の管電流値より低減してスキャンする際に、X線管の回転速度が変わっても、X線管電流の変調制御における応答特性を考慮して、X線管電流を所望した通りに低減できるX線CT装置を実現させる。【解決手段】X線管の回転速度を設定する回転速度設定手段107と、X線管電流を所定の管電流値より低減すべきX線管の回転角度範囲αを設定する回転角度範囲設定手段105と、設定された回転速度(周期)Tおよび回転角度範囲αを基に、被検体をX線CTスキャンする際のX線管の回転角度θと管電流値k(θ)・A(θ)との関係を決定する関係決定手段108と、被検体をX線CTスキャンする際に、決定された関係に従ってX線管電流を変調させる変調手段111とを備えたX線CT装置とする。【選択図】図2
