X-ray image processing method and device for performing that method in which a portion corresponding to an x-ray absorption filter is selectively processed

摘要

An image processing method is provided to remove areas from an image made by x-irradiation, said areas corresponding to absorption filters in the x-ray beam. Because such filters, also known as x-ray shutters, are inserted into the x-ray beam from the outside of the x-ray beam, x-ray shutter-areas extend from the periphery of the image. Therefore, once the edge of an x-ray shutter-areas has been determined, the part of the image located between the periphery and the x-ray shutter- edge is removed. X- ray shutter-edges are determined by locating transition-points in the image having brightness-transitions having maxima of both the first and second spatial derivatives of the brightness- value. An x-ray shutter-edge is then determined by fitting a curve through the transition-points. The curve fitting is performed with the use of weight-factors that are representative of the likelihood that a transition-point is on an actual x-ray shutter-edge. This likelihood is larger for transition-points which are closer to the periphery of the image, for transition-points having low image roughness towards the periphery of the image. Furthermore, a transition-point having a large height of its brightness-transition is more likely to be on an actual x- ray shutter-edge.