The present invention relates to medical X-ray imaging. In order to provide further facilitated positioning of a medical X-ray imaging apparatus, a device (10) for support in positioning a medical X-ray imaging apparatus is provided. The device comprises an input unit (12), a processing unit (14) and an output unit (16). The input unit is configured to receive a 3D motion-model of a currently used X-ray imaging apparatus； and to receive a 3D model of a subject suitable for a calculation of virtual X-ray projections. The input unit is also configured to receive current 3D spatial context data in relation to a current location and orientation of the X-ray imaging apparatus, the 3D spatial context data comprising at least one of the group of a current arrangement of an object support, a current position of the subject on the object support, and objects or persons currently located in a potential moving area of the X-ray imaging apparatus. The input unit is further configured to receive movement instructions for movement of the 3D motion-model. The processing unit is configured to adapt the 3D motion-model according to the movement instructions. The processing unit is also configured to generate a virtual X-ray projection of a region of interest based on the spatial arrangement of the 3D motion-model in relation to the 3D model of the subject. Further, the output unit is configured to provide image data of the virtual X-ray projection.
