Computed-tomography apparatus and control method thereof

Abstract

A computed-tomography apparatus acquires a cross-sectional image of an object from projection data obtained by scanning the object with radiation while rotating a scanner around the object. One of rotation positions of the scanner having a smaller attenuation of radiation is determined. The operation of the scanner is controlled to start the scan from the rotation position having the smaller attenuation. Individual weights are assigned to projection data in a predetermined rotation angle range near a scan start rotation position of the scanner and near a scan end rotation position thereof and projection data in a rotation angle range opposite to the predetermined rotation angle range, respectively. The weighted projection data and unweighted projection data are used for determining corrected data for the entire circumference of the object to generate a cross-sectional image based thereon. The range of a correction region can be changed in accordance with a scan start position so that when the scan start position is not suited in a direction having a smaller attenuation, the correction region is narrowed to optimize the effect of suppression of background noises and artifacts. A plurality of scan start positions can be set on the locus of scan rotation of the scanner so that the actual scan is started from the scan start position which is first detected after the point of time when a scan start signal is given.