Patent Number: 053655664
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a radiation diaphragm of the type having a diaphragm lamella engaged by an adjustment system, so that the lamella is adjustable in the ray beam of a radiation transmitter. 2. Description of the Prior Art European Application 0 373 285 discloses a gating device for an x-ray diagnostics installation which includes a rigid element that is adjustable around a longitudinal axis in a plane perpendicular to the useful ray beam, and which has an arcuate edge. As a result of the variable arrangement of the arcuate edge, the useful ray beam can be individually matched to (gated onto) an arcuately shaped examination subject. German OS 35 00 812 discloses a gating mechanism for x-radiation which includes rigid diaphragm lamellae adjustable into the ray beam, these lamellae lying against one another parallel to both sides of a slot, and being individually adjustable in the longitudinal direction by an adjustment system dependent on the size of a subject. In angiographic examinations, for example of the legs of a patient, x-radiation is incident on regions of an image intensifier, used as the radiation receiver, which are not shadowed by the legs directly. Those regions may comprise a relatively large-area. The excessively high radiation intensity in these regions leads to a degradation of the image quality due to reduction of contrast and glare; moreover, the stray radiation is unnecessarily increased. In order to counter these negative effects, diaphragms, for example of sheet lead, are employed, which are laterally moved into the beam path so that they are matched as well as possible to the contours of the examination subject. This gating is suitable in order to blank the ray beam at the sides of the legs. Strip-shaped diaphragms having a fixed shape that are arranged in the region between the legs are employed for blanking radiation that is incident on the image intensifier between the legs. It is also possible to provide plastically deformable and absorbent volumes, for example sacks of rice flour, in this region. This technique, however, is difficult to manipulate and increases the stray radiation. SUMMARY OF THE INVENTION It is an object of the present invention to implement a radiation diaphragm of the type having a lamella adjustable by an adjustment system, such that the radiation that is incident directly on the radiation receiver, and is thus unattenuated, is blanked as well as possible. This object is achieved in accordance with the principles of the present invention in a radiation diaphragm wherein the diaphragm lamella is flexible, preferably composed of elastic material, and wherein means are provided for flexing the diaphragm lamella so that radiation absorption can be well-matched to examination subjects that differ in shape. Preferably, elements of the adjustment system engage the diaphragm lamella such that the diaphragm lamella is adjustable around an axis aligned perpendicularly relative to the central ray of the ray beam, since the effective width of the diaphragm lamella can thus be set in a continuum within a broad range. For use within an examination subject not having any straight limiting lines but instead having only contours curved, the adjustment system preferably engages end faces of the diaphragm lamella lying opposite one another, and the end faces are adjustable along the aforementioned axis and toward one another. The diaphragm lamella can thus be well-matched to arcuate examination subjects. An improved adaptability of the diaphragm lamella to different examination subjects is achieved in an embodiment wherein the adjustment system includes first and second holders for the diaphragm lamella which are adjustable independently of one another. The adjustment possibilities of the diaphragm lamella are thus enhanced. Preferably the diaphragm lamella is composed of rubber containing lead oxide since it is thus extremely flexible and has a high radiation absorption. The diaphragm lamella may be composed of a plurality of sub-lamellae, or a plurality of elastic diaphragm lamellae may be provided that are adjustable relative to one another, thereby enhancing the adaptability of the diaphragm lamella to examination subjects having different shapes.