Method of determining the spatial response signature of a two dimensional X-ray detector comprising a photostimulable phosphor by - generating a flat field image by homogeneously exposing said detector to radiation and scanning the homogeneously exposed detector and by digitizing the scanned image, - generating a low-pass filtered version of said flat field image, by applying a pixel-centered background average kernel to said flat field image, - background demodulating said flat field image by dividing its pixel values by the corresponding pixel values in the low-pass filtered version, - wherein the signature is obtained by processing multiple flat field images generated for the same detector, - wherein said flat field images are spatially registered at the detector surface and wherein a reference flat field image for spatial warping is selected such that the maximum angular difference between the flat field images obtained by said scanning of said reference image and any other image of the set images acquired for said detector, is minimal, - wherein a register vector map is calculated by cross-registering a multitude of spatially distributed markers arranged in the detector surface and present in each flat-field image, - wherein said markers are virtual markers which consist of a neighbouring pixel-cluster defined within said reference flat-field image, - wherein a bidirectional marker-grid is defined in the reference flat-field image, - wherein interpolation or extrapolation of the data in said register vector map is used to compose a warp vector map which links each pixel of said reference flat-field image to its physically associated location in the other flat-field images, - wherein each flat-field image is warped to correspond pixel-wise with the reference flat-field image by interpolating or extrapolating the pixel signal at the positions indicated by the corresponding warp vector map such that pixel signals of the warped image have been calculated at the same position on the detector surface as the signals of their corresponding pixels in the reference image, - wherein bi-directionally decoupled, sub-pixel phases from said register vector map are extracted and an anisotropic convolution filter kernel is distilled from it to re-establish the sharpness of the warped image at the level before warping, - wherein a median averaged value of all corresponding pixels from the set of sharpness re-established, warped flat-field images is selected as signature pixel. - generating a flat field image by homogeneously exposing said detector to radiation and scanning the homogeneously exposed detector and by digitizing the scanned image, - generating a low-pass filtered version of said flat field image, by applying a pixel-centered background average kernel to said flat field image, - background demodulating said flat field image by dividing its pixel values by the corresponding pixel values in the low-pass filtered version, - wherein the signature is obtained by processing multiple flat field images generated for the same detector, - wherein said flat field images are spatially registered at the detector surface and wherein a reference flat field image for spatial warping is selected such that the maximum angular difference between the flat field images obtained by said scanning of said reference image and any other image of the set images acquired for said detector, is minimal, - wherein a register vector map is calculated by cross-registering a multitude of spatially distributed markers arranged in the detector surface and present in each flat-field image, - wherein said markers are virtual markers which consist of a neighbouring pixel-cluster defined within said reference flat-field image, - wherein a bidirectional marker-grid is defined in the reference flat-field image, - wherein interpolation or extrapolation of the data in said register vector map is used to compose a warp vector map which links each pixel of said reference flat-field image to its physically associated location in the other flat-field images, - wherein each flat-field image is warped to correspond pixel-wise with the reference flat-field image by interpolating or extrapolating the pixel signal at the positions indicated by the corresponding warp vector map such that pixel signals of the warped image have been calculated at the same position on the detector surface as the signals of their corresponding pixels in the reference image, - wherein bi-directionally decoupled, sub-pixel phases from said register vector map are extracted and an anisotropic convolution filter kernel is distilled from it to re-establish the sharpness of the warped image at the level before warping, - wherein a median averaged value of all corresponding pixels from the set of sharpness re-established, warped flat-field images is selected as signature pixel.