Patent Number: 053655664
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a transillumination image of an examination subject, for example legs 1. Regions in which the radiation of a radiation transmitter 6 (shown in FIG. 2) would be incident directly on a radiation receiver (not shown) i.e., unattenuated regions, are identified with reference numerals 3, 4 and 5. Since the radiation directly incident on these regions 3, 4 and 5 results in an undesirable over-drive of the radiation receiver, such as an image intensifier, a radiation diaphragm 8 constructed in accordance with the invention is arranged in the beam path of the ray beam 7 of the radiation transmitter 6 between the radiation transmitter 6 and the examination subject, as shown in FIG. 2. This radiation diaphragm 8 includes first and second diaphragm lamellae 9 and 10 that are laterally adjustable into the ray beam 7 for occluding the first and third regions 3 and 5. A third diaphragm lamella 11 is inventively composed of elastic material and is arranged between the first and second diaphragm lamellae 9 and 10. This third diaphragm lamella 11 serves the purpose of occluding the radiation that would be incident in the second region 4. In order to be able to vary the effective width of the third diaphragm lamella 11, it is adjustable around an axis 12 aligned perpendicularly relative to the central ray of the ray beam 7. Preferably, the third diaphragm lamella 11 is also adjustable in the plane perpendicular to the central ray of the ray beam 7, so that its alignment can be matched better to the examination subject. In the embodiment of FIGS. 3, 4 and 5 adjustment means in the form of holders 15 and 16 are attached at opposite end faces 13 and 14 of the third diaphragm lamella 11, the diaphragm lamella 11 being adjustable around the axis 12 by means of holders 15 and 16, One holder 16 can be stationary while the other holder 15 is adjustable around the axis 12. Preferably, however, both holders 15 and 16 are adjustable around the axis 12 in the same direction or in opposite directions. FIGS. 4 and 5 show exemplary shapes the third diaphragm lamella can assume when the holders 15 and 16 are adjusted around the axis 12. For examinations wherein it is desired that the third diaphragm lamella 11 arcuately gate a region, the holders 15 and 16 are adjustable along the axis 12 and toward one another, as shown in FIG. 6. The radiation diaphragm of the invention can include a diaphragm lamella 17 shown in FIG. 7. The lamella 17 may be used in place of the lamella 11 and is likewise elastic, and has a mushroom-shaped cut-out, so that the ray beam 7 can be gated to correspond to the head of an examination subject. In order to enable the gating of the ray beam 7 corresponding to different head shapes, adjustment elements 19a and 20a of an adjustment system engage the fourth diaphragm lamella 17 at respective sides 19 and 20, aligned perpendicularly relative to one another. As shown in FIG. 8, the radiation diaphragm of the invention can include diaphragm lamella 21 formed by a plurality of sub-lamellae 22 through 29, mounted on an adjustment element 37 so that the alignment of the sub-lamellae 22 through 29 in the ray beam 7 is individually adjustable. FIG. 9 shows a diaphragm lamella 30 of the radiation diaphragm of the invention, formed by individual lamellae 31 through 33 that are aligned parallel to one another and are mounted on an adjustment element 38 so as to be adjustable relative to one another. It is thus possible to give the diaphragm lamella 30 different shapes. The adjustment system for the diaphragm lamellae 11, 17, 21 and 30 can have an electromechanical drive, for example an electric motor that engages the diaphragm lamellae 11, 17, 21 or 30 via a belt or a lever articulation guided in bearings for the adjustment thereof. The diaphragm lamellae 11, 17, 21 and 30 are preferably composed of an elastic material, for example rubber containing lead oxide, however, they can alternatively be composed of metal sheets arranged in a scale-like pattern. In accordance with the invention, the first and second diaphragm lamella 9 and 10 can likewise be flexible, such as composed of an elastic material, and can be rotatably and/or tiltably seated in the beam path by a correspondingly executed holder. The radiation diaphragm of the invention is preferably arranged optimally close to the radiation source 7, since it thus has a small, economical structure. The radiation diaphragm, however, must have dimensions such that the diaphragm lamellae have an adequate thickness for radiation absorption. The area of the diaphragm projection can be varied by varying the spacing relative to the focus of the radiation transmitter 6. The alignment of the diaphragm lamellae in the ray beam 7 can ensue in various ways. Due to the versatility of the elastic diaphragm lamellae, a user-friendly, automatic diaphragm alignment based on the content of a video system following the image intensifier can be implemented in addition to manual setting with visible auxiliary radiation. For automatic alignment of the diaphragm lamellae, only a brief-duration drive of the radiation transmitter 6 with low energy is then required, so that the radiation stress on the examination subject is low. In accordance with the invention, the diaphragm lamella of the radiation diaphragm can be executed as an elastic filter lamella which, for example, can assume the shapes shown in FIGS. 10 through 13. The filter lamella 33 is composed of an elastic plate engaged by holders 34 and 35 at at least two sides lying opposite one another for the alignment in the ray beam 7 of the radiation transmitter 6. The holders 34 and 35 are held in the adjustment system such that the desired alignment of the filter lamella 33 can be effected. An arcuate alignment of the filter lamella 33 is achieved as shown in FIG. 10, by adjusting the holders 34 and 35 in the direction to the central ray 36 of the ray beam 7 and/or obliquely relative thereto. The alignment of the filter lamella 33 shown in FIG. 11 is achieved by adjusting the holders 34 and 35 in different planes perpendicularly aligned relative to the central ray 36, and in the direction to the central ray 36. An alignment of the filter lamella 33 according to FIG. 12 is achieved by maintaining one holder, for example, the holder 34, stationary, and adjusting the holder 35 in a plane differing from the plane of the holder 34, and which is obliquely aligned relative to the central ray 36. In the alignment of the filter lamella 33 shown in FIG. 13, the holders 34 and 35 are arranged in the same plane but are obliquely aligned relative to the central ray 36. FIGS. 10 through 13 also show a diagram in which the radiation intensity I following the filter lamella is indicated. Holders of the adjustment system can likewise be provided at further sides of the filter lamella 33 lying opposite one another Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.