X-ray collimator
An x-ray collimator that may include a substrate containing a plurality of holes, each hole being frustoconical at one end and tubular at the other end for use in an x-ray imaging system, whereby the x-ray collimator may be aligned with a two-dimensional array of x-ray sources and a two-dimensional x-ray sensor, and whereby x-ray photons from the x-ray sources may pass through the collimator holes and emerge as a beam of x-ray photons in a narrow angle cone which may pass through a subject being imaged, positioned between the output holes of the collimator and the x-ray sensor.
1. An x-ray collimator, comprising:
a substrate containing a plurality of collimator holes, wherein at least some of said collimator holes comprise along their axial lengths an entrance hole through which x-rays may pass into the collimator hole, a tapered portion being frustoconical, and a following tubular portion having an output hole, the x-ray collimator further comprising x-ray target material comprising a first thin sheet of high atomic number material and being arranged to convert, in use, electrons from an array of electron emitters into localized sources of x-ray photons, such that each of said at least some collimator holes emits a beam of x-ray photons emerging from the output hole in a narrow angle cone being approximately parallel or having an angle of deviation from parallel in the range 1 to 20 degrees.
2. The x-ray collimator of claim 1 , wherein the plurality of collimator holes are arranged in a two dimensional array.
3. The x-ray collimator of claim 1 , wherein the substrate is made from silicon or a glass.
4. The x-ray collimator of claim 3 , wherein the glass is made from fused silica.
5. The x-ray collimator of claim 1 , wherein the tapered portions comprise an approximate parabolic shape.
6. The x-ray collimator of claim 5 , wherein the parabolic shape comprises an approximate “Winston Cone” shape.
7. The x-ray collimator of claim 1 , wherein the tubular portion is cylindrical.
8. The x-ray collimator of claim 1 , wherein the distance between the entrance hole and the output hole of the tubular portion is substantially greater than the diameter of the output hole.
9. The x-ray collimator of claim 1 , wherein the distance between the entrance hole and the output hole of the tubular portion is at least ten times greater than the diameter of the output hole.
10. The x-ray collimator of claim 1 , wherein the collimator holes running through the substrate are lined on their inner surface with a thin film.
11. The x-ray collimator of claim 10 , wherein the thin film comprises at least a single layer of either tungsten or iridium.
12. The x-ray collimator of claim 10 , wherein the thin film comprises a bi-layer of one of tungsten and aluminium oxide, tungsten and silicon, and tungsten and carbon.
13. The x-ray collimator of claim 10 , wherein the thin film comprises a bi-layer combination of a high Z number metal and a low Z number and low density spacer material.
14. The x-ray collimator of claim 1 , wherein each of the portion holes is abutted against the target material.
15. The x-ray collimator of claim 14 , wherein the first thin sheet comprises one or more of tungsten, tungsten alloy, molybdenum or gold.
16. The x-ray collimator of claim 14 , wherein the first thin sheet of the target material has a thickness of approximately of 1 to 5 μm.
17. The x-ray collimator of claim 14 , wherein a second thin sheet of x-ray filter material is positioned between the target material and each of the entrance holes.
18. The x-ray collimator of claim 17 , wherein the x-ray filter material is made from aluminium.
19. The x-ray collimator of claim 17 , wherein the x-ray filter material has a thickness of approximately 100 to 500 μm.
20. A method of obtaining an x-ray image, comprising:
emitting x-ray photons from an x-ray source such that at least some of the x-ray photons pass through one or more collimator holes of an x-ray collimator and emerge in a narrow angle cone of x-ray photons, at least some of which pass through a subject positioned between the collimator and a two-dimensional x-ray sensor, wherein the x-ray collimator is aligned with the two-dimensional x-ray sensor, and wherein the one or more collimator holes comprise along their axial lengths an entrance hole through which the x-rays may pass into the collimator hole, a tapered portion being frustoconical, and a following tubular portion having an output hole, the x-ray collimator further comprising x-ray target material comprising a first thin sheet of high atomic number material and being arranged to convert, in use, electrons from an array of electron emitters into localized sources of x-ray photons.