PROBLEM TO BE SOLVED: To provide an X-ray CT system which has less deviation of CT values or artifacts by compensating a variation in the sensitivity compensation data of an X-ray detector element accompanying a beam position variation during a measurement by the scanner rotation speed or the tilting angle of the X-ray CT system.SOLUTION: This X-ray CT system is equipped with a conversion value calculating means, an air compensation data converting means, and a projection data compensating means. The conversion value calculating means measures each air compensation data 2 for a period of time S1 and a tilting angle A1 of a scanner which serves as a reference, and a rotational period of time Sm and a tilting angle Am of scanners other than the reference scanner in advance, and calculates a conversion value to the air compensation data for the rotating period of time Sm and the tilting angle Am of the scanner from the air compensation data for the rotational period of time S1 and the tilting angle A1 of the scanner. The air compensation data converting means converts the air compensation data 1 for the rotating period of time S1 and the tilting angle A1 of the reference scanner which is obtained by a daily measurement by using the calculated conversion value into the air compensation data which is used for the air compensation of the main measurement. The projection data compensating means compensates the projection data for the main measurement by using the converted air compensation data.COPYRIGHT: (C)2008,JPO&INPIT【課題】X線CT装置のスキャナ回転速度やチルト角度による計測中のビーム位置変動に伴うX線検出器素子の感度補正データの変動を補正し、CT値のずれやアーチファクトが少ないX線CT装置を提供する。【解決手段】基準とするスキャナの回転時間S1とチルト角度A1、基準以外のスキャナの回転時間Smとチルト角度Amの各エア補正データ2を予め計測し、スキャナの回転時間S1とチルト角度A1のエア補正データからスキャナの回転時間Smとチルト角度Amのエア補正データへの変換値算出手段と、算出した変換値を用いて日常的な計測で得られる基準のスキャナの回転時間S1とチルト角度A1のエア補正データ1から本計測のエア補正に用いるエア補正データに変換する手段と、変換されたエア補正データを用いて本計測の投影データを補正する手段を備えている。【選択図】図1
