X-ray imaging apparatus, X-ray imaging method and method of controlling X-ray imaging apparatus

• US 8,214,158 B2
• Filed: 03/11/2009
• Issued: 07/03/2012
• Est. Priority Date: 03/12/2008
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Mukaide, Taihei, Takada, Kazuhiro, Watanabe, Masatoshi
• Primary Examiner(s): Charioui, Mohamed
• Assistant Examiner(s): Desta, Elias
• Application Number:
  US12/526,418
• Publication Number:
  US 20100318302A1
• Time in Patent Office: 1,210 Days
• Field of Search: 702/28, 702/172, 702/189, 382/132, 378/53, 378/62, 378/210
• US Class Current: 702/28
• CPC Class Codes: A61B 6/484 involving phase contrast X-ray imaging
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G01N 23/083 the radiation being X-rays
• CPC Class Codes: G01N 23/20 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
• CPC Class Codes: G21K 1/10 Scattering devices; Absorbing devices; Ionising radiation filters
• CPC Class Codes: G21K 2207/005 Methods and devices obtaining contrast from non-absorbing interaction of the radiation with matter, e.g. phase contrast

Abstract

A simplified X-ray imaging apparatus is capable of computationally determining effective atomic numbers with small error factors even for light elements. In one embodiment, the X-ray imaging apparatus has an X-ray generation unit 101 (400) for generating X-rays and a detector 105 (405) for detecting X-rays transmitted through an object of examination 104 (403). A computing unit 106 (406) computationally determines a quantity of an X-ray phase attributable to the object of examination and an X-ray transmittance of the object of examination from data detected by the detector. The computing unit also computationally determines an effective atomic number of the object of examination from ρ_et determined from the quantity of the X-ray phase and μt determined from the X-ray transmittance.

Claims

1. An X-ray imaging apparatus comprising:

an X-ray generation unit for generating X-rays;

an X-ray dividing element for spatially dividing X-rays emitted from said X-ray generation unit;

a detector for detecting X-rays divided by said X-ray dividing element and transmitted through an object of examination; and

a computing unit for computationally determining an X-ray shift amount attributable to the object of examination and an X-ray transmittance of the object of examination from data detected by said detector and further computationally determining an effective atomic number of the object of examination from ρ

_et (ρ

_e;

electron density, t;

thickness of the object of examination) determined from the X-ray shift amount and μ

t (μ

;

linear attenuation coefficient) determined from the X-ray transmittance.

2. The X-ray imaging apparatus according to claim 1, wherein said computing unit computationally determines the effective atomic number on the basis of μ

/ρ

_e computationally determined from the ρ

_et and the μ

t.

3. The X-ray imaging apparatus according to claim 1, further comprising:

a moving mechanism for synchronously moving said X-ray generation unit, said X-ray dividing element and said detector.

4. The X-ray imaging apparatus according to claim 3, wherein said computing unit computationally determines the electron density of the object of examination by way of image reconstruction from the ρ

_et.

5. The X-ray imaging apparatus according to claim 4, wherein the image reconstruction is realized by means of a filtered back-projection method.

6. The X-ray imaging apparatus according to claim 1, wherein said computing unit computationally determines a differential phase contrast image of the object of examination, using a positional shift amount obtained by comparing detected positions of X-rays observed in a state where the object of examination is not present and detected positions of X-rays transmitted through the object of examination and a distance between the object of examination and the detector.

7. The X-ray imaging apparatus according to claim 6, wherein said computing unit obtains an X-ray phase contrast image of the object of examination by integrating the differential phase contrast image.

8. The X-ray imaging apparatus according to claim 1, wherein said X-ray dividing element is an element having two-dimensionally arranged holes.

9. The X-ray imaging apparatus according to claim 1, wherein said X-ray dividing element is formed by using a material selected from platinum, gold, lead, tantalum and tungsten.

10. The X-ray imaging apparatus according to claim 1, further comprising:

a display unit for displaying information on the effective atomic number of the object of examination computationally determined by said computing unit.

11. The X-ray imaging apparatus according to claim 1, further comprising:

an object moving mechanism for moving the object of examination.

12. The X-ray imaging apparatus according to claim 1, further comprising:

a monochromator arranged between said X-ray generation unit and said X-ray dividing element to monichromatize X-rays.

13. An X-ray imaging method comprising:

a step of generating X-rays by means of an X-ray generation unit;

a step of spatially dividing the X-rays by means of an X-ray dividing element;

a step of detecting the X-rays divided by the X-ray dividing element and transmitted through an object of examination by means of a detector; and

a step of computationally determining an X-ray shift amount attributable to the object of examination and an X-ray transmittance of the object of examination from data detected by the detector and further computationally determining an effective atomic number of the object of examination from ρ

_et (ρ

_e;

electron density, t;

thickness of the object of examination) determined from the X-ray shift amount and μ

t (μ

;

linear attenuation coefficient) determined from the X-ray transmittance.

14. A method of controlling an X-ray imaging apparatus, comprising:

a step of controlling an X-ray generation unit to generate X-rays;

a step of controlling an X-ray detector to detect the X-rays that were divided by an X-ray dividing element and subsequently transmitted through an object of examination;

a step of controlling a computing unit to computationally determine an X-ray shift amount attributable to the object of examination and an X-ray transmittance of the object of examination; and

a step of computationally determining an effective atomic number of the object of examination from ρ

_et (ρ

_e;

electron density, t;

thickness of the object of examination) determined from the X-ray shift amount and μ

t (μ

;

linear attenuation coefficient) determined from the X-ray transmittance.

15. An X-ray imaging apparatus comprising:

an X-ray generation unit for generating X-rays;

a detector for detecting X-rays emitted from said X-ray generation unit and transmitted through an object of examination;

a computing unit for computationally determining a quantity of an X-ray phase attributable to the object of examination and an X-ray transmittance of the object of examination from data detected by the said detector and further computationally determining an effective atomic number of the object of examination from ρ

_et (ρ

_e;

electron density, t;

thickness of the object of examination) determined from the quantity of the X-ray phase and μ

t (μ

;

linear attenuation coefficient) determined from the X-ray phase transmittance.

16. The X-ray imaging apparatus according to claim 15, further comprising an X-ray dividing element for spatially dividing X-rays emitted from said X-ray generation unit, and obtaining the quantity of the X-ray phase from an X-ray shift amount obtained by using said X-ray dividing element.

17. The X-ray imaging apparatus according to claim 15, further comprising a monochromator for monochromatizing X-rays emitted from said X-ray generation unit and an analyzer crystal arranged between the object of examination and said detector, and obtaining the quantity of the X-ray phase from a refraction angle of X-ray obtained by using said analyzer crystal.

18. An X-ray imaging method comprising:

a step of detecting X-rays transmitted through an object of examination, using an X-ray detector;

a step of computationally determining a quantity of an X-ray phase attributable to the object of examination and an X-ray transmittance of the object of examination from data detected in the detection step; and

a step of computationally determining an effective atomic number of the object of examination from ρ

_et (ρ

_e;

electron density, t;

thickness of the object of examination) determined from the quantity of the quantity of the X-ray phase and μ

t (μ

;

linear attenuation coefficient) determined from the X-ray transmittance,

wherein said steps of computational determination are carried out by means of a computational unit.

19. The X-ray imaging method according to claim 18, wherein the quantity of the X-ray phase attributable to the object of examination is determined from an X-ray shift amount obtained by using an X-ray dividing element for spatially dividing X-rays.

20. The X-ray imaging method according to claim 18, wherein the quantity of the X-ray phase attributable to the object of examination is determined by a refraction angle of X-ray obtained by using an analyzer crystal.