Image composition method and imaging apparatus for performing said method

Abstract

Sub-images are merged in order to form an assembled image representing an elongate scene. In order to counteract artifacts in the assembled image such as disturbing transitions at the boundaries of adjacent sub-images in the image assembly method in accordance with the invention, pixel-values of overlapping portions of consecutive sub-images are interpolated so as to form pixel-values of the assembled image. The relative shift between consecutive sub-images with respect to the elongate scene is calculated from image information contained in the sub-images themselves. Correlations of pixel-values in overlapping portions of consecutive sub-images are determined as a function of the shift-value of the shift between consecutive sub-images with respect to the elongate scene. The actual shift between consecutive sub-images is found as the shift-value for which the correlation attains its maximum-value. The image assembly method in accordance with the invention is particularly suitable for use in peripheral x-ray angiography. Consecutive sub-images are made by x-irradiations of e.g. a patient's leg with an x-ray imaging system comprising an x-ray source, an x-ray detector, in various positions relative to the patient. In order to induce a sufficient amount of contrast in the sub-images to enable the determination of the relative shift between consecutive sub-images the invention proposes to image a contrasting object together with the elongate scene itself. Preferably the contrasting object has the form of a ruler with a binary pattern which may be incorporated in the patient table.