The lowest dose is usually used in order to create fluoroscopic x-ray images during navigation using the guide wire and the catheter and/or during the use of a stent as well as during vascular imaging. This low dose results in a very low signal-to-noise ratio so that the image quality is extremely restricted.
To improve the image quality, temporal and/or local filterings are implemented. The temporal filtering is disadvantageous in that movement blurrings and double images appear. The local low pass filtering is known as an alternative here, in which a distortion of the objects, for instance the vessel edges, is to be accepted.
DE 103 09 166 A1 discloses an x-ray diagnostic device, which has a device for detecting edges in x-ray images and a device for filtering the individual x-ray images along these edges. Here the direction of the filtering is determined, with the used filter mask remaining fixed. One disadvantage of this directional filtering consists in artificial structures, e.g. so-called swirls and/or worm threads possibly developing in homogenous noise regions. Such filters can thus only be used in restricted filter strengths.