Reconstruction method of tilted three-dimensional X-ray CT image

摘要

PPROBLEM TO BE SOLVED: To provide a method of reconstituting an image in inclined three- dimensional X-ray CT (computer tomography) for arbitrarily selecting an irradiation angle of X-rays. PSOLUTION: An object to be measure is irradiated with X-rays at an angle smaller than 90 with respect to a rotational-axis direction of the object so as to be three-dimensionally reconstituted on the basis of detected image data. Its reconstitution algorithm includes a step in which an X-ray focal point, a distance up to the rotation center of the measuring object, and a distance up to a detection face are expressed as a function of the rotation angle of an X-ray source, in which an obtained image is turned by a tomographic angle so as to be converted into a vertical-surface image, and in which also an intensity of the image is converted according to a distance; a step in which projection data is multipled by a weighting factor so as to create weighted projection data; a filtering step in which a filter function and the weighted projection data are Fourier-transformed so as to perform a convolution computing operation; and a step in which the filtered weighted projection data is back-projected on a three-dimensional reconstitution space. PCOPYRIGHT: (C)2004,JPO