Patent Number: 046637745
Section: summary

BACKGROUND OF THE INVENTION 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. SUMMARY OF THE INVENTION 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.