Patent Number: 047529474
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS A primary radiation diaphragm 3 is shown in FIG. 1 for use in gating an X-ray beam 2 generated at an X-ray focus, schematically indicated at 1. The primary diaphragm 3 includes a rectangular diaphragm system 4 having a pair of diaphragm plates 5 and 6 disposed in a plane and adjustable in opposite directions relative to each other, and another pair of diaphragm plates 5a and 6a disposed in a plane spaced from the plane containing the plates 5 and 6, the plates 5a and 6a also being mounted for adjustable movement in opposite directions relative to each other. The upper diaphragm plates 5a and 6a are synchronously moved in combination to a slightly greater extent then are the plates 5 and 6 with respect to a central ray 7 of the X-ray beam 2 so as to permit, if needed, diverging of the beam 2 as indicated in FIG. 1. Two further pairs of diaphragm plates are also included within the diaphragm system 4 movable in opposite directions which are perpendicular to the directions of movement of the diaphragm pairs 5a and 6 a and the diaphragm pair 5 and 6. One plate 8 and one plate 8a of these additional pairs of plates are shown in FIG. 1. The plates 8 and 8a, and the corresponding plates in each pair (not shown) limit the extent of the X-ray beam 2 in a direction perpendicular to the plane of FIG. 1. The primary diaphragm 3 also includes an iris diaphragm 9 disposed in front of the rectangular diaphragm system 4 in the direction of beam propagation. The iris diaphragm 9 adapts the shape of the X-ray beam 2 to the shape of the input luminescent screen of an X-ray image intensifier (not shown) by inserting wedges at the corners of the rectangular diaphragm system 4, as needed. Two diaphragm plates 10 and 20 are shown in FIG. 3 with the surrounding parts and mountings omitted for clarity. Those details are shown in FIGS. 2 and 3 discussed below. The diaphragm plates 10 and 20 are adjustable in opposite directions relative to the central ray 7 in two different parallel planes so that the plates 10 and 20 can be moved past each other over each other. The path of adjustment of the diaphragm plates 10 and 20 is thus large enough so that each diaphragm plate 10 and 20 can selectively limit the X-ray beam 2 with one of its two edges, those two edges being disposed perpendicular to the path of adjustment of the plates. For example, diaphragm plate 10 has a left edge 15 which may be selectively contoured, and a right edge 14, which may be straight. The primary radiation diaphragm 3 also has a light sight including a light source 12 and a mirror 13 which is transmissive for x-radiation. The mirror 13 generates a visible light field which is coextensive with the X-ray field so that the extent of the gated X-ray field can be seen on the examination subject. The gating of the X-ray beam 2 by the diaphragm plates 10 and 20 is achieved as more clearly seen in FIGS. 2 and 3. In FIG. 2, more clarity only the left diaphragm plate 10 is shown. The plate 10 is shown at a left extreme position in dashed lines and at a right extreme position in dot and dashed lines in FIG. 2. A diaphragm plate 10 is mounted on an annular disc 11 and is displaceable along a slot 12 in the disc 11. The plate 10 is guided in the slot 12 by two pegs 13. The slot 12 is of a length such that the X-ray beam 2 can be optionally limited by the straight right edge 14 of the plate 10, or by the curved left edge 15 of the diaphragm plate 10. The maximum diaphragm aperture is defined by a rectangular opening 16 in the disc 11. As can be seen in FIGS. 2 and 3, the diaphragm plate 10 can be moved from the left extreme position to the right extreme position, in which case the curved edge 15 limits the X-ray beam 2. The different shapes of edges and 14 permit the gated field to similarly exhibit a different shape, dependent upon the position of the diaphragm plate 10. The edge 15 functions to gate the beam to a shape corresponding to the heart contour, and as stated above, is curved for this purpose. The edge 14 is a straight line. In a known manner, the diaphragm plate 10 is bevelled at its regions close to the edge, and is thus partially transparent to x-radiation. The diaphragm plate 20 (not shown in FIG. 2) is a mirror image of the plate 10. Adjustment of the diaphragm plate 10 (as well as the plate 20 by a similar mechanism) is undertaken by a pin 17 mounted to the plate 10 which is moved in an oblong opening of a disc 19 disposed beneath the disc 11. The disc 19, as well as a disc 22 disposed above the disc 11, has a central opening for defining the maximum field size. The disc 22 has not been shown in FIG. 2. The disc 22 also has a radial slot, in which a pin 23 of the diaphragm 20 is displaceably guided. For adjusting the diaphragm plates 10 and 20, a relative rotation of the discs 19 and 22 relative to the disc 11 is undertaken. When all three discs 11, 19 and 22 are rotated congruently and synchronously, the position of the gated slot is also rotated. The discs 11, 19 and 22 are provided with outside denticulation, schematically indicated by the dashed line inside the circumference of the disc 11 in FIG. 2, so as to be individually or synchronously rotated. The pins 17 and 23 are mounted to shoulders of the diaphragm plates 10 and 20. The shoulders are bent downwardly or upwardly at right angles to the remainder of the plates. The diaphragm plates 10 and 20 can be moved completely past one another so as to selectively limit the X-ray beam 2 with one of the two edges of the plates. These are the two edges referenced 14 and 15 for the diaphragm plate 10. As stated above, the diaphragm plate 20 is a mirror image of the diaphragm plate 10, that is, the straight edge is at the left in the position shown in FIG. 3, and the edge matched to the heart contour is at the right as shown in FIG. 3. 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 modificatons as reasonably and properly come within the scope of their contribution to the art.