FAN-SHAPED X-RAY BEAM IMAGING SYSTEMS EMPLOYING GRADED MULTILAYER OPTIC DEVICES

• US 20120051499A1
• Filed: 08/30/2010
• Published: 03/01/2012
• Est. Priority Date: 08/30/2010
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Lee, Susanne Madeline, Edic, Peter Michael, Hopkins, Forrest Frank
• Granted Patent: US 8,311,184 B2
• Time in Patent Office: Days
• US Class Current: 378/16
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4021 involving movement of the focal spot
• CPC Class Codes: A61B 6/4078 Fan-beams
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G21K 1/062 Devices having a multilayer structure
• CPC Class Codes: G21K 2201/064 having a curved surface

Abstract

An X-ray imaging system that produces one or more fan-shaped beams is described. The system includes a target for emitting X rays that includes at least one target focal spot, and one or more graded multilayer optic devices in optical communication with the target. The optics transmits at least a portion of the source X rays to produce the one or more fan-shaped beams. The graded multilayer optic devices include at least a first graded multilayer section for redirecting and transmitting X rays through total internal reflection. The graded multilayer section includes a high-index layer of material having a first complex refractive index n₁, a low-index layer of material having a second complex refractive index n₂, and a grading zone disposed between the high-index and low-index layers of material. The grading zone includes a grading layer having a third complex refractive index n₃ such that Re(n₁)>Re(n₂)>Re(n₃).

Claims

1. An X-ray imaging system that produces one or more fan-shaped beams, comprising:

a target for emitting X rays upon being struck by electrons from an electron source, said target comprising at least one target focal spot; and

one or more graded multilayer optic devices in communication with said target to transmit at least a portion of said X rays through total internal reflection to produce said one or more fan-shaped beams, said graded multilayer optic devices, comprising;

a first graded multilayer section for redirecting and transmitting X rays through total internal reflection including,

a high-index layer of material comprising a first complex refractive index n₁ having a real part Re (n₁) and an imaginary part β

₁;

a low-index layer of material comprising a second complex refractive index n₂ having a real part Re (n₂) and an imaginary part β

₂; and

a grading zone disposed between said high-index layer of material and said low-index layer of material, said grading zone having a grading layer comprising a third complex real refractive index n₃ having a real part Re (n₃) and an imaginary part β

₃ such that Re(n₁)>

Re(n₃)>

Re(n₂).

2. The system of claim 1, wherein said target is enclosed within a housing having an X-ray transparent window, said graded multilayer optic devices are mounted within the housing, mounted external to the housing, fabricated as the window, or integrated into the window.

3. The system of claim 1, wherein said one or more graded multilayer optic devices is mounted on said target for transmission targets or proximate to said target for reflection targets.

4. The system of claim 1, wherein said fan-shaped beam comprises a continuous fan-shaped beam or a discrete stack of parallel fan-shaped beams.

5. The system of claim 1, wherein said graded multilayer optic devices each have a collection angle of up to about 90 degrees.

6. The system of claim 1, wherein said one or more graded multilayer optic devices comprise a circular cross-sectional profile, and wherein the graded multilayer optic devices are arranged in one or two two-dimensional array to produce said one or more fan-shaped beams.

7. The system of claim 1, wherein each of the graded multilayer optic devices has a rectangular cross-sectional profile.

8. The system of claim 7, wherein said one or more graded multilayer optic devices comprises pairs of stacked graded multilayer optic devices, wherein one half of a pair is positioned to be a mirror image of the other half of the pair.

9. The system of claim 1, wherein said one or more graded multilayer optic devices are configured to compensate for movement of said at least one focal spot on said target.

10. The system of claim 1, wherein said X-ray imaging system is employed in one of a computed tomography (CT) system, an X-ray radiographic system, a tomosynthesis system, or an X-ray diffraction system.

11. The system of claim 1, wherein a ratio of a change in an imaginary part (β

) of a complex refractive index to a change in a decrement (δ

) from unity of a real part (1−

δ

) of a complex refractive index between adjacent multilayer materials is a minimum.

12. The system of claim 1, wherein the grading zone comprises a plurality of layers.

13. A multi-energy X-ray imaging system that produces one or more fan-shaped beams, comprising:

an electron source;

a target for forming X rays upon being struck by electrons from said electron source;

a vacuum chamber housing the target;

a window through which the X rays may exit the vacuum chamber;

at least one graded multilayer optic device configured to transmit a desired range of X-ray energies to produce the one or more fan-shaped beams, said at least one graded multilayer optic device comprises;

a first optic portion for redirecting first optic X rays through total internal reflection; and

a second optic portion for redirecting second optic X rays, said second optic X rays being at a different mean energy level than said first optic X rays.

14. The multi-energy X-ray imaging system of claim 13, wherein:

said first optic portion is configured for producing a spectrum with a high mean energy; and

said second optic portion is configured for a spectrum with a low mean energy, wherein the mean energy of said first optic energy spectrum is greater than or equal to the mean energy in the said second optic energy spectrum.

15. The multi-energy imaging system of claim 13, comprising a filtering mechanism for filtering out certain energies from a beam transmitted by said at least one optic device, wherein said filtering mechanism is at least one of a filtering mechanism external to said optic device and a filtering mechanism integral to said optic device.

16. A method for imaging an object, comprising:

emitting electron beams from at least one electron beam emitter towards a target having at least one target focal spot;

producing X rays from the target in response to being struck by the electron beams;

forming the X rays into one or more fan-shaped beams, wherein the fan-shaped beams are produced via total internal reflection of the X rays through one or more graded multilayer optic devices positioned such that at least one of the one or more graded multilayer optic devices is in optical communication with the at least one target focal spot; and

generating an image of the object by using the emitted X rays transmitted via the one or more graded multilayer optics.

17. The method of claim 16, further comprising filtering at least a portion of an energy spectrum.

18. The method of claim 16, further comprising two-dimensional (2D) reconstruction computations that are used to generate an image of the object.

19. The method of claim 16, further comprising performing computed tomography, tomosynthesis, X-ray diffraction or X-ray radiography of the object.

20. The method of claim 16, further comprising performing diffraction analysis and identifying at least one of the crystal structure, composition, and stress/strain of the object.