Radiographic apparatus and an image processing method therefore

摘要

Initial values A^1P^1M^1 . . . A^nP^nM^n of parameters representing a geometric relationship between an X-ray tube, a stage and a flat panel X-ray detector are estimated, a least squares solution (p^W)i of characteristic point three-dimensional coordinates is estimated, and only limited parameters are updated until reprojection square errors converge. Thus, based on known radiographic conditions, initial values of the parameters are estimated, and a nonlinear optimization operation is carried out on only the parameters considered, in view of mechanisms and drive characteristics of the apparatus, to have large errors between the initial values of the parameters and the parameters at a time when radiography is actually carried out. As a result, the calculation can be speeded up, while securing the convergence accuracy of the nonlinear optimization operation, by using the radiographic conditions, i.e. information on tomography.

主权项

1. A radiographic apparatus for performing radiography, comprising:
a stage for holding an object; and an x-ray radiation emitting device and an x-ray radiation detecting device arranged opposite each other across the stage; the radiography being performed based on projection images obtained by detecting, with the x-ray radiation detecting device, x-ray radiation emitted from the x-ray radiation emitting device and transmitted through the object; the apparatus further comprising: a driving device for driving at least one of the x-ray radiation emitting device and the stage in a state where the object or a phantom for correction is placed on the stage; a parameter calculating device for calculating parameters representing a geometric relationship among the x-ray radiation emitting device, the stage and the x-ray radiation detecting device by nonlinear optimization operation based on a plurality of projection images of the phantom for correction; a slice image calculating device for calculating slice images of the object based on a plurality of projection images of the object and the parameters, and when carrying out the calculation, reconstructing the images using those of the parameters suited to radiographic conditions at a time of radiographing the object; and a number of parameters limiting device for reducing and limiting, when calculating the parameters, the number of parameters calculated by nonlinear optimization operation, based on radiographic conditions at a time of radiographing the phantom for correction, wherein only the parameters limited are updated when the parameters are updated.