X-Ray Diagnostics Installation With Rotatable Support Plate

1. Field of the Invention

The present invention relates to X-ray diagnostics installations, and in particular to a support plate for an examination subject for such an installation.

2. Description of the Prior Art

X-ray diagnostic installations are known for the production of mammography exposures having a support plate for supporting the patient's breast, the support plate having a receptacle chamber for receiving an X-ray film cassette, and a secondary radiation grid overlying the receptacle such that the grid is disposed between the examination subject and the cassette. A compression means may also be provided above the support plate.

In such conventional installations, the secondary radiation grid attenuates the secondary radiation emerging from the examination subject, however, has the disadvantage of increasing the distance between the subject and the film in the cassette. Additionally, in some instances it is preferable to make exposures without the use of a secondary radiation grid.

It is an object of the present invention to provide an X-ray diagnostic installation having a support plate with a secondary radiation grid which can be optionally positioned with the secondary radiation grid disposed in front of or behind the X-ray film cassette contained in the support plate.

The above object is inventively achieved in a support plate for an X-ray diagnostics installation which is mounted so as to be rotatable about an axis which is perpendicular to a central ray of the X-ray beam. The secondary radiation grid is disposed on one side or surface of the support plate, and the X-ray cassette is contained in a chamber with the secondary radiation grid overlying the chamber on one side. The support plate can be rotated so as to dispose the secondary radiation grid over or in front of the X-ray cassette in the direction of beam propogation, such that the secondary radiation grid is between the examination subject and the cassette, and can be rotated such that the secondary radiation grid is beneath or behind the cassette in the direction of beam propogation. X-ray exposures without the use of the secondary radiation grid can thus be produced in a simple manner by pivoting or rotating the support plate. The secondary radiation grid is relatively mechanically sensitive, and need not be removed from the support plate, as in conventional installations, in order to make this type of exposure.

In a further embodiment of the invention, a radiation detector for providing a signal to an automatic exposure control unit may be disposed at the side of the support plate facing away from the radiation grid. The radiation detector thus receiving the radiation dose following the X-ray film in the direction of beam propogation. When an X-ray film cassette is inserted into the chamber for exposure without the secondary radiation grid, in which case the support plate is rotated such that the secondary radiation grid is disposed behind the X-ray film cassette in the direction of beam propogation, the exposure time can also be controlled by the automatic exposure unit. If a specific side of the radiation detector must be exposed to the X-ray beam, the radiation detector may be mounted so as to be rotatable about an axis which is substantially parallel to the axis of revolution of the support plate, or is coincident therewith, so that the necessary side of the detector can be rotated so as to have the X-ray beam incident thereon.

FIG. 1 is a side schematic view of an X-ray diagnostics installation constructed in accordance with the principles of the present invention.

FIG. 2 is a perspective view of a support plate for an X-ray diagnostics installation constructed in accordance with the principles of the present invention in a first position.

FIG. 3 is a perspective view of a support plate for an X-ray diagnostics installation constructed in accordance with the principles of the present invention rotated 180.degree. from the position shown in FIG. 2 to a second position.

FIG. 4 is a perspective view of a support plate for an X-ray diagnostics installation constructed in accordance with the principles of the present invention having a rotatable radiation detector.

FIG. 5 is a perspective view of a further embodiment of a support plate for an X-ray diagnostics installation constructed in accordance with the principles of the present invention with a rotatable radiation detector.

An X-ray installation constructed in accordance with the principles of the present invention is schematically shown in FIG. 1 consisting of an X-ray tube 1 for generating an X-ray beam 2 which passes through a primary beam diaphragm 3. An exposure subject, such as the breast of a female patient to be examined, is supported on a support plate 4 and may be compressed by a compression plate 6 which is movable in the direction of a central ray 5 of the X-ray beam 2. The support plate 4 is rotatable about an axis 7, which is substantially perpendicular to the central ray 5, as indicated by the curved double arrow 8. The support plate 4 has a secondary radiation grid on one side thereof, described in greater detail below, and rotation of the support plate 4 permits the secondary radiation grid to be optionally positioned above or below a film cassette contained within the support plate 4.

Further details of the support plate 4 are shown in FIGS. 2 and 3, which show the two exposure positions of the support plate 4. The support plate 4 has a lateral chamber or receptacle 9 for receiving an X-ray film cassette 9a. The support plate 4 has a secondary radiation grid 10 disposed on one side thereof. With the support plate 4 in the position shown in FIG. 2, the secondary radiation grid 10 is disposed in front of the exposure chamber 9, and thus in front of the film cassette therein, in the direction of beam propogation. The lamellae of the secondary radiation grid 10 are directed to the focus of the X-ray tube 1 and accordingly suppress radiation scatter proceeding from the exposure subject.

The support plate 4 is rotatably seated on an angled arm 11 so as to be pivotable about the axis 7. Pivoting the plate 4 in the direction of the arrow 8a shown in FIG. 2 places the plate 4 in the position shown in FIG. 3 wherein the secondary radiation grid 10 is disposed behind the chamber 9 as seen in the radiation direction. In order to decrease the distance between the examination subject and the X-ray film cassette, the X-ray film cassette may be inserted in a compartment 12 of the support plate 4, the compartment 12 being beneath the support plate 4 when the support plate 4 is in the position shown in FIG. 2. An X-ray exposure can thus be undertaken without the intervening secondary radiation grid 10. A minimum subject/film distance is accordingly achieved. Rotation of the support plate 4 in the direction of arrow 8b returns the support plate 4 to the position shown in FIG. 2.

The support plate 4 may, as shown in FIG. 3, be provided on the side thereof facing away from the secondary radiation grid 10 with a radiation detector 13. The radiation detector 13 may provide a signal to an automatic X-ray exposure control unit for automatically setting an optimum exposure time.

Radiation detectors such as the radiation detector 13 normally have one surface on which the radiation must be incident. Accordingly, in the embodiment shown in FIG. 4 the radiation detector 13 is mounted on an arm 14 having a gimbal joint 14a. The arm 14 and the radiation detector 13 are normally contained in a recess 15 in one side of the support plate 4. The joint 14a permits the radiation detector 13 to be moved in the direction of double arrow 21 to the position 13a indicated by dot and dashed lines. When in position 13a, the radiation detector 13 can then be rotated as indicated by the double arrow 16 to place the proper side of the radiation detector facing the radiation beam.

A further embodiment of a support plate 4 constructed in accordance with the principles of the present invention is shown in FIG. 5, wherein the radiation detector 13 is disposed in a recess 17 on the side of the support plate facing away from the radiation grid 10. The radiation detector 13 is mounted on an arm 18 which permits the detector 13 to be withdrawn toward the front of the plate 4 as indicated by the double arrow 19. Once withdrawn, the radiation detector 13 can then be rotated as indicated by the curved double arrow 20 to place the appropriate side of the detector 13 such that the X-radiation is incident thereon. The radiation detector 13 is then reinserted in the receptacle 17. It is also possible to expose the radiation detector 13 by moving the plate 4, instead of the detector 13.

FIG. 4 shows the support plate 4 positioned for generating an exposure without the use of the secondary radiation grid, corresponding to that shown in FIG. 3. FIG. 5 shows the plate 4 positioned for obtaining an exposure with the secondary radiation grid 10, corresponding to FIG. 2.

The exposure chamber 9 in the support plate 4 accepts a standard X-ray film cassette having dimensions, for example, of approximately 24.times.30 cm. A slightly larger cassette can be accommodated in the compartment 12. The support plate 4 may be dimensioned such that a cassette inserted into the compartment 12 projects slightly beyond the front edge of the support plate 4. By so doing, the approach of the cassette to the exposure subject is not impeded by the support plate 4, that is, the edge of the film cassette can be placed directly against the thorax of the patient so that the exposure subject is completely imaged on the X-ray film.

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.