Patent ID: 7764763

Claim:
An X-ray computed tomography (CT) system comprising: an X-ray source for radiating X-rays; an X-ray detector disposed opposite to said X-ray source with a predetermined rotation center axis therebetween, and comprising a plurality of detector elements arranged two-dimensionally in a Z-axis direction, which is a direction along said rotation center axis, and a direction crossing said Z-axis direction; a data acquisition unit for acquiring X-ray detection data detected by said plurality of detector elements of said detector; scan means for causing said data acquisition unit to acquire said X-ray detection data detected by said detector by radiating X-rays from said X-ray source at each of rotational angles, while causing said X-ray source and said detector to rotate around said rotation center axis; and reconstruction means for performing an arithmetic operation, in which two-dimensional projection data obtained by processing the acquired X-ray detection data are back projected along a second path different in said Z-axis direction from a first path of X-rays at the time of said detection, to reconstruct an image, wherein a focal position of said X-ray source is constructed such that it is alternately movable on plus and minus sides in said Z-axis direction for each of said rotational angles, wherein projection data that are acquired at either position of the alternate movements of a focus of said X-ray source are arranged with a sampling pitch s iso along the Z-axis direction at said rotation center axis, and wherein quantities of the alternate movements of the focus of said X-ray source are determined so that, when Z-axis direction arrangement positions of respective projection data obtained at said alternate focal positions are away by α iso (positive value) times s iso at said rotation center axis from a Z-axis direction arrangement position of projection data obtained when the focus is at a middle point between the alternate focal positions, said α iso becomes a value less than ¼ and greater than 0.