An apparatus for assisting with positioning of an implant on a specific point in a vessel of a patient is proposed. A first interventional instrument is inserted in a region of the specific point. A series of 2D x-ray recordings of the vessel with the first instrument are obtained by adjusting an x-ray device. Based on markers of the first instrument mapped in the 2D x-ray recordings, at least two reference lines are defined restricting the specific point. A second interventional instrument is inserted in the region of the specific point. Fluoroscopy images of the vessel with the second instrument are obtained by adjusting the x-ray device. The reference lines in the fluoroscopy images are superimposed as localization aid. The specific point in the vessel can also be restricted by a reference region as a localization aid defined based on x-ray recordings of the specific point obtained using contrast agent.