Abstract: The present invention relates to an apparatus (10) for scan direction detection and stitching sequence determination of a plurality of X-ray images, comprising: an input unit (20); a processing unit (30); and an output unit (40). The input unit is configured to provide the processing unit with a first X-ray image acquired by an X-ray image acquisition system, and the first image comprises image data of a patient. The input unit is configured to provide the processing unit with a second X-ray image acquired by the X-ray image acquisition system after it has moved with respect to the patient, and the second image comprises image data of the patient. The processing unit is configured to determine a top similarity value comprising a comparison of at least one region of image data of the patient at and/or adjacent to a top border in the first image with at least one equivalent sized region of image data of the patient at and/or adjacent to a bottom border in the second image.