The invention relates to an imaging apparatus for imaging an object (3) being preferentially a catheter. A kinematics model (12) of a robot representing the object (3), which is defined by kinematics parameters, and projection data of the object (3), which correspond to different projection directions, are provided. The kinematics model (12) is modified by modifying the kinematics parameters such that a difference between simulated projection data, which are determined by simulating a forward projection of the kinematics model (12), and the provided projection data is minimized. Since the object (3) is represented by a kinematics model (12) of a robot, movements of the object (3), in particular, deformations of the object (3), can be described in a simple way by few kinematics parameters, thereby allowing modifying the model (12) and, thus, following a movement of the object fast by modifying the few kinematics parameters, in particular, in real-time.