X-ray radiography method and system

DETAILED DESCRIPTION When a chest is imaged several times, generally the shape of the heart differs in a plurality of images due to pulse of the heart and therefore also positions of the mediastinum and the lungs differ.
As the result, an image discontinuity, for example, the difference between the edge position of the heart on the right image and that on the left image, takes place at junctions in a joined image.
Such a joined image gives rise to inconveniences in diagnosis.
By the method described in JP-A-2-10636 cited previously for suppressing variations in the pin-cushion type distortion characteristics, since it is necessary to adjust the potential applied to the electrodes, every time the distance between the X-ray tube and the X-ray image intensifier is varied and also every time the electronic view field is enlarged, much time and work are required.
Therefore it is very troublesome to realize this method.
Further, by the method described in JP Utility Model-A-Hei5-28316 cited previously, by which images are corrected in an electronic manner, since the sampling points are inputted manually by means of the digitizing system or the mouse, it is difficult to measure distortion with a high precision and also automation thereof is difficult.
Furthermore, by the two prior art techniques it is difficult to correct distortion so that the error of distortion correction is less than one pixel size on the whole image.
Therefore the prior art techniques are hardly applied to image processing, for which precise distortion correction is required, such as joining of images obtained by a plurality of imagings or reconstruction of a three-dimensional image.
The present invention has been made in view of the situation described above and the object thereof is to provide an X-ray radiography method capable of solving the problems of the prior art techniques as described above, by which it is possible to obtain a plurality of images in same phase stages as cardiac movement and to effect joining of images with a high precision by eliminating discontinuity at areas around joining lines in a joined image and a chest having an area larger than a view field of an X-ray detector can be imaged with a high spatial resolving power by carrying out image distortion correction processing in a region reaching ends of the view field of the X-ray detector so that the images hold precise positional information over the whole view field of the X-ray detector, and a system for realizing same