PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus reducing image quality deterioration caused by an in-vivo indwelling object made of metal.SOLUTION: This X-ray CT apparatus 1 sectionalizes a scanographic image for alignment into sections of a high absorbent body, a low absorbent body and others from a density distribution of the scanographic image, and obtains a position or a shape of the high absorbent body. The X-ray CT apparatus 1 estimates a substance of the high absorbent body based on a known X-ray attenuation coefficient of a portion except the high absorbent body, an irradiation X-ray dose, and a measured transmitted X-ray dose. The X-ray CT apparatus 1 calculates an optimum irradiation X-ray dose in a photographic range included with the high absorbent body based on the X-ray attenuation coefficient corresponding to the distribution of the high absorbent body and the estimated substance, and performs real photography of a test subject according to the irradiation X-ray dose.COPYRIGHT: (C)2012,JPO&INPIT【課題】 金属製の体内留置物による画質劣化を低減することが可能なX線CT装置を提供する。【解決手段】 X線CT装置1は、位置決め用のスキャノ画像の濃度分布から高吸収体、低吸収体、その他の区分に区分化し、高吸収体の位置や形状を求める。高吸収体以外の部分の既知のX線減弱係数と、照射X線量と、計測された透過X線量とに基づいて、高吸収体の物質を推定する。また、高吸収体の分布及び推定された物質に該当するX線減弱係数に基づいて、高吸収体が含まれる撮影範囲について最適な照射X線量を算出し、その照射X線量に従って被検体の本撮影を行う。【選択図】図3
