X-RAY CONVERTER ELEMENT

Abstract

An x-ray converter element has an x-ray-permeable and moisture-impermeable substrate, an x-ray-permeable carrier that is connected to the substrate, and a scintillator that is applied on the substrate, and an optically-transparent and moisture-impermeable protective layer that covers the scintillator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of an x-ray converter element in schematic section view.

FIG. 2 shows a second embodiment of an x-ray converter element in schematic section view.

FIG. 3 shows characteristic lines for the transmission of various substrates, carriers and combinations thereof, dependent on x-ray energy, as well as a typical x-ray spectrum for general radiography.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the x-ray converter element shown in FIGS. 1 and 2 an x-ray-permeable and moisture-impermeable substrate is designated with 1 that is formed of aluminum and advantageously exhibits a layer thickness of 300 μm.

According to the invention the substrate 1 is connected to an x-ray-permeable carrier 2 that is composed of carbon fiber-reinforced plastic and advantageously exhibits a layer thickness of 1000 μm.

A scintillator 3 that includes Csl:Tl (cesium iodide doped with thallium) and exhibits a layer thickness of (advantageously) 500 μm is applied on the substrate 1.

The scintillator 3 is protected by an optically-transparent and moisture-impermeable protective layer 4.

In the exemplary embodiments shown in FIGS. 1 and 2, the substrate is connected to the carrier 2 by an x-ray-permeable adhesive layer 5.

In accordance with the invention, the substrate 1 can be smaller than the carrier 2 (see FIG. 1) or exactly as large as the carrier 2 (see FIG. 2). In the exemplary embodiment according to FIG. 1, no forces (from screwing or clamping) act on the substrate 1 for affixing the x-ray converter element. An x-ray radiation (designated with 6 in FIGS. 1 and 2) initially radiates through the x-ray-permeable carrier 2 in order to subsequently pass through the adhesive layer 5 and the x-ray-permeable and moisture-impermeable substrate 1 and generate visible light in the scintillator 3. The visible light generated in the scintillator 3 exits through the optically-transparent and moisture-impermeable protective layer 4. The light image so generated is projected onto a CCD camera with the aid of imaging optics. The CCD camera transduces the light image into electrical signals. The electrical signals are subsequently processed further and output as a digital image.

Various transmissions dependent on the x-ray energy are shown in FIG. 3. The characteristic line of the transmission of aluminum with a layer thickness of 1000 μm is designated with 200. The characteristic line of the transmission of a 2000 μm-thick layer made from amorphous carbon is designated with 300. The characteristic line of the transmission for a composite made from 300 μm aluminum and 1000 μm carbon fiber-reinforced plastic is designated with 400.

Furthermore, a characteristic line of a typical x-ray spectrum (designated with 100) of general radiography after passage of the x-ray radiation through a human body is shown for assessment of the transmission properties of the various substrates, carriers or, respectively, combinations, whereby the human body was simulated by 3 mm aluminum and 15 cm PMMA (polymethylmethacrylate, known as “Plexiglass”).

The x-ray quanta have energies greater than 40 keV. For these x-ray energies the transmission of the composite made from 300 μm aluminum and 1000 μm carbon fiber-reinforced plastic (characteristic line 400) is slightly higher than that of 2000 μm amorphous carbon (characteristic line 300).

In the range between 30 and 40 keV there is no noteworthy contribution to the x-ray spectrum (characteristic line 100). The transmission properties in this x-ray energy interval are thus important. In this x-ray energy interval the permeability of the composite made from 300 μm aluminum and 1000 μm carbon fiber-reinforced plastic (characteristic line 400) is distinctly better than the permeability of 1000 p aluminum (characteristic line 200) and comparable with the permeability of 2000 μm amorphous carbon (characteristic line 300).

Only a small portion of the x-ray energy is present in the range smaller than 30 keV, meaning that the transmission properties in this range are of subordinate importance. In this range the usage of 2000 μm amorphous carbon (characteristic line 300) instead of the composite made from 300 μm aluminum and 1000 μm carbon fiber-reinforced plastic (characteristic line 400) brings slightly higher transmission values. The practical value for the image quality is slight, however.

The inventive composite made from the carrier 2 and the substrate 1 essentially satisfies three requirements. It represents in an ideal manner a suitable substrate for the process of the scintillator coating (increased temperatures and vacuum) and simultaneously offers a sufficient mechanical stability, whereby the incident x-ray radiation is only insignificantly attenuated in the relevant range of the x-ray energy (see FIG. 3).

In contrast, the solutions according to the prior art utilize as the substrate and the carrier a single body that must satisfy all three requirements. As explained in the preceding, this does not operate in a particularly satisfactory manner.

Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.

Claims

1. An x-ray converter element comprising: an x-ray permeable and moisture-impermeable and moisture-impermeable substrate;an x-ray permeable carrier connected to said substrate;a scintillator applied on said substrate; andan optically-transparent and moisture-impermeable protective layer covering said scintillator.

2. An x-ray converter as claimed in claim 1 wherein said substrate is comprised of aluminum.

3. An x-ray converter as claimed in claim 1 wherein said substrate has a thickness in a range between 20 μm and 600 μm.

4. An x-ray converter as claimed in claim 3 wherein said substrate has a thickness of 300 μm.

5. An x-ray converter as claimed in claim 1 wherein said carrier is comprised of carbon fiber-reinforced plastic.

6. An x-ray converter element as claimed in claim 1 wherein said carrier has a thickness in a range between 500 μm and 2500 μm.

7. An x-ray converter element as claimed in claim 6 wherein said carrier has a thickness of 1000 μm.

8. An x-ray converter as claimed in claim 1 comprising an x-ray permeable adhesive layer connecting said carrier and said substrate.

9. An x-ray converter element as claimed in claim 8 wherein said adhesive layer has a thickness in a range between 10 μm and 200 μm.

10. An x-ray converter element as claimed in claim 1 wherein said scintillator is comprised of at least one material selected from group consisting of Csl:Tl, Csl:Na and Nal:Tl.

11. An x-ray converter as claimed in claim 1 wherein said scintillator is comprised of a material comprising at least one alkali halogenide.

12. An x-ray converter as claimed in claim 1 wherein said scintillator has a thickness of 500 μm.

13. An x-ray converter element comprising: an x-ray-permeable and moisture-impermeable substrate comprised of aluminum;an x-ray-permeable carrier comprised of carbon fiber-reinforced plastic;an x-ray-permeable adhesive layer connecting said substrate and said carrier;a scintillator applied on said substrate; andan optically-transparent and moisture-impermeable protective layer covering said scintillator.

14. An x-ray converter element as claimed in claim 13 wherein said substrate has a thickness in a range between 20 μm and 600 μm, said carrier has a thickness in a range between 500 μm and 250 μm, said adhesive layer has a thickness in a range between 10 μm and 200 μm, and said scintillator has a thickness of 500 μm.