Image systems in radiology are sometimes full of mistakes which can have several reasons:

• reproduction geometry (size and form of focal spot, geometric magnification of the object)
         
  as well as

• system blurring, like foil blurring and insufficient pressure on the film-foil-system, electron-optical defects of image amplifiers as well as defects of the lens systems and the different receivers. Concerning electron-optics and lens systems, we must differentiate between errors on the basis of astigmatism, image field curvature, spherical aberration, chromatic aberration, defocusing, but also,

• motional blurring, e.g. caused by vibrations.

    In order to determine the reduction in quality of the image relay, and to control the optical chain or individual links of the optical chain a multitude of tests and test processes were developped. Tests made of x-ray absorbing material, which are described below, are especially tried and tested. Their handling is simple and easy to repeat. On the one hand it allows a quick survey of the resolution quality, but on the other hand it offers the possibility to find additional interesting quality parameters by further evaluations.