PROBLEM TO BE SOLVED: To solve the problem that when merely obtaining an image by using only energy of a small range close to monochrome, influence of beam hardening can be removed but count is reduced in a narrow window and a statistics error is increased and the removal cannot be attained by a present X-ray tube performance and data of each window has to be added (averaged) in some form, and that even when performing weighed averaging at the time of counting, remarkable control of the beam hardening is followed by side reaction of raising a weighing function of only a narrow energy portion, that is, increasing the influence of statistics noise.SOLUTION: An image reconstruction method for an X-ray CT device subjects a count measured values obtained in a plurality of energy windows to transformation to the line integral of an X-ray linear attenuation coefficient and thereafter to weighed averaging.COPYRIGHT: (C)2010,JPO&INPIT【課題】単に単色に近い狭い範囲のエネルギーだけ用いて画像を得てもビームハードニングの影響を除去できるが、これは狭いウィンドウではカウントが減り、統計誤差が大きくなるため現状のX線管性能では実現できず、ウィンドウごとのデータを何らかの形で加算(平均化)する必要がある。カウントの時点で重み付け平均を行っても、ビームハードニングを顕著に抑制するためには狭いエネルギー部分のみの重み付け関数を高くする、すなわち統計ノイズの影響を大きくする副作用が伴う。【解決手段】複数のエネルギーウィンドウで得られたカウント計測値に対し、X線線減弱係数の線積分に変換した後に、重み付け平均化を行うことを特徴とするX線CT装置の画像再構成手法。【選択図】図2
