The invention addresses the problem of correctly positioning a catheter and reducing radiation doses. It relates to an X-ray imaging system (1) for a robotic catheter, comprising said catheter (3), and a processing unit (5) for receiving X-ray images of a patient environment (15). By being adapted to receive one or more auxiliary information items and using said information for determining the catheter position, the processing unit does not entirely have to rely on a large number of scanned image data, thus helping to reduce radiation while correctly delivering the catheter position as a function of as few as a single image, preferably 2D, and said one auxiliary information items. Further, said processing unit allows for at least one of rendering an image and provide said image to a visualization device (21), and providing feedback, e.g. steering commands, to said robotic catheter.