X-ray tube assembly with beam limiting device for reducing off-focus radiation

A beam limiting apparatus for reducing the emission of off-focus radiation from an x-ray tube assembly, wherein the x-ray tube assembly comprises a housing including an x-ray port for the passage of x-rays therethrough, a first mounting surface formed adjacent to the x-ray port, an x-ray tube mounted within the housing and including an evacuated envelope, an anode mounted within the envelope, and a cathode spaced relative to the anode within the envelope, wherein the anode defines a target surface, the cathode projects onto the target surface a focal spot defining a first size and shape, the x-ray port is spaced relative to the focal spot for receiving x-radiation emitted therefrom, and the x-ray port and envelope define a first predetermined depth therebetween, the beam limiting apparatus comprising:

• a peripheral flange defining a second mounting surface locatable over the first mounting surface of the housing for fixedly securing the beam limiting apparatus to the housing;
• a radiation-absorbing body projecting outwardly from the peripheral flange and receivable through the x-ray port, the radiation-absorbing body defining a base surface, an x-ray entrance aperture formed through the base surface, an x-ray exit aperture spaced relative to the x-ray entrance aperture, and an x-ray transmissive beam conduit formed between the entrance and exit apertures, wherein the base surface extends into the housing a second depth less than the first depth with the base surface spaced closely adjacent to the evacuated envelope of the x-ray tube and defining a predetermined gap therebetween, the radiation-absorbing body is formed of a substantially electrically nonconductive, filled polymeric material, the x-ray entrance aperture defines a second size and shape, the x-ray exit aperture defines a third size and shape, and the second and third sizes and shapes are selected to define an x-ray beam of predetermined corresponding size and shape.