A method and system for reconstructing image data obtained from plural sequential exposures of an object by a radiation source through a multiple slit beam scanning assembly, wherein frames of original image data in the form of plural pixels are obtained for each discrete scanning step/exposure and a minimum pixel value of at least one frame is determined. Based on this determined minimum value, a cutoff value is determined. The pixel values of each frame are compared with the cutoff value, and the image is reconstructed by summation of all the pixel image data above the cutoff value for each respective pixel. In order to improve spatial resolution, the slit width of the scanning assembly is selected be the narrower than the pixel size. Pixel image data produced by exposure from radiation passing through the same slit of the scanning assembly in consecutive scanning steps are then assigned to adjacent pixels in a direction perpendicular to the scanning beam of an enlarged pixel matrix. To achieve a balanced aspect ratio, pixel values for pixels in a direction parallel to the scanning beam are assigned by interpolation between pixel values assigned in the perpendicular direction.