an x - ray examination apparatus includes a beam diaphragm with an x - ray absorbing shutter which is arranged between the x - ray source and the x - ray detector in order to intercept parts of the x - ray beam , thus forming a limited x - ray beam . the shutter can be displaced according to different degrees of freedom by different rotations of control rings whereto the shutter is coupled . because the shutter can be moved to practically any desired position within the x - ray beam , the beam diaphragm can shape the cross - section of the limited x - ray beam in such a manner that essentially only a part of a patient to be examined is exposed to x - rays .