A panel system for a radiation source as well as apparatus and methods for receiving a projected image and determining a relative position between a radiation source and a radiation detector

The present invention relates to a diaphragm system (3) for a radiation source (1) and to an apparatus and a method for receiving a projection image (7) and for determining a relative position between a radiation source (1) and a radiation detector (2) of the projection image (7 ). The diaphragm system (3) for producing the projection image (7) of a on the radiation detector (2) imaged object (4) by one from the radiation source (1) emitted, the shutter system (3) by running beams (5), wherein the diaphragm system (3 ) has a radiopaque marker (20) with at least one reference structure (19), characterized in that the marker (20) on the diaphragm system (3) is arranged such that a central ray (6) of the beam (5) (the shutter system 3 happens) unimpeded and the reference structure (19) always by a shadow in the projection image (7) of the object (4) is visible for determining a contrast of the shadow of the reference structure (19) in the projection image (7), wherein the contrast of the shadow in the projection image (7) by a maximum absorption of radiation on the reference structure (19) is maximized.