Positional Stability of 2D X-ray Images for Computer Tomography

摘要

Recently X-ray Computer Tomography (XCT) has made its introduction in the 3D geometrical quality control of industrial parts. The step from medical to industrial CT recommends a much higher accuracy of the CT process. Part of the accuracy is determined by the accuracy of the 2D radiographic images used to digitally reconstruct the scanned object. This paper discusses a method for improving the stability of the 2D X-ray image position. This method is than tested on an industrial part, on a 225 kV CT machine. The positional stability is mainly influenced by the spot stability of the X-ray source. This spot can drift due to wear of the target or heat fluctuations inside the source. The compensations of the drift of the 2D images are on one hand based on temperature measurements of the X-ray source and on the other hand based on calibration spheres measured together with the part. The techniques used in this paper can be applied to any 3D X-ray CT scan and are easy to implement. To conclude a comparison is made between the original scan of an industrial part and the compensated scan to give an idea of how much this stability influences the whole scanning process. This paper gives a better insight into some errors occurring during the X-ray CT process and can contribute to the accuracy improvement of the XCT process.