Tomographic X-ray apparatus for producing tomographic images

Claim 1

In a tomographic X-ray apparatus for producing tomographic images of an exposure object, including an X-ray measuring arrangement having an X-ray source generating an X-ray beam for transilluminating said exposure object, whose cross-sectional spread perpendicular to the X-rayed layer is equal to the layer thickness and in parallel with the layer is equal to or lesser than said layer thickness, and an X-radiation receiver for measuring radiation intensity behind said object at successive equidistant points; drive means for said measuring arrangement, said drive means including a pivot mounting for producing rotary movements of said X-ray measuring arrangement through small equidistant angular increments about a rotational axis generally coincident with the symmetrical longitudinal axis of said exposure object, a slide carriage mounted on said pivot mounting for imparting a linear scanning movement to said X-ray measuring arrangement peripendicular to the direction of said X-ray beam across the expanse of said object in alternative sequence with each said incremental angular movement; and holding means for said exposure object in the path of said X-rays including a box-shaped compensating member of tissue-equivalent material fixedly connected with said pivot mounting and encompassing said exposure object, said compensating member being homogeneous and uniformly absorbent in the X-ray direction and having an extent in the direction of scan movement equal to or larger than the scan movement, and an elastic contouring member resting opposite said compensating member adapted to rigidly lie against said exposure object upon the introduction of the latter into said compensating member, the improvement comprising: said compensating member being constituted of a rigid plastic material of tissue-equivalent density; a cylindrical recess in said compensating member extending symmetrically to the rotational axis of said pivot mounting; said contouring member including a rigid plastic material ring of tissue-equivalent material slidably located in said recess in closely-fitted relationship therewith; an elastically expandable hose being fastened to the inner side of said ring; and controllable pumping means being connected to said hose for pumping water thereinto for positioning said hose against said exposure object, said compensating member and said ring of tissue-equivalent material being permeated by the X-ray beam from said X-ray source, said pumping means comprising an airtight, water-filled pressure receptacle connected to and located below said hose, an overflow receptacle connected to and located below said hose, said pressure receptacle including a displacement member interiorly thereof expandable through pumping in of pressurized air, an air pressure generator connected with said displacement member through a control valve, an overflow conduit connected to the highest point of said hose, a flow valve connecting said overflow conduit with said overflow receptacle, a flow-off conduit connecting said overflow receptacle with said pressure receptacle, a shutoff valve in said flow-off conduit, a switch for opening said control valve and flow valve during actuation of said pumping means and concurrently closing said shutoff valve, a level switch in said overflow receptacle for closing said flow valve upon reaching of a selected water level in said overflow receptacle, and a delay element being operatively associated with said flow valve for delaying closure thereof during water return outflow from said hose.