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.La présente invention concerne l'imagerie médicale à rayons X. Afin de fournir un positionnement facilité d'un appareil d'imagerie médicale à rayons X, un dispositif (10) pour l'assistance au positionnement d'un appareil d'imagerie médicale à rayons X est présenté. Le dispositif comprend une unité d'entrée (12), une unité de traitement (14) et une unité de sortie (16). L'unité d'entrée est configurée pour recevoir un modèle de mouvement 3D d'un appareil d'imagerie à rayons X actuellement utilisé ； et pour recevoir un modèle 3D d'un sujet a
