SYSTEM AND METHOD FOR DETERMINING THE COMPOSITION OF AN OBJECT

• US 20110249788A1
• Filed: 04/07/2011
• Published: 10/13/2011
• Est. Priority Date: 04/08/2010
• Status: Abandoned Application

• Current Assignee: CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement
• Original Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Inventors: NÜESCH, Joachim, Seitz, Peter
• Application Number:
  US13/081,754
• Publication Number:
  US 20110249788A1
• Time in Patent Office: Days
• US Class Current: 378/53
• 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 23/087 using polyenergetic X-rays
• CPC Class Codes: G01V 5/20 Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects

Abstract

The present invention discloses a method for identifying the elemental composition of an object (120) characterized by comprising the following procedures: (210) selecting an energy range of an irradiation energy range according to at least one energy-selection criterion to obtain a selected energy range; (215) selecting, according to at least one element-selection criterion, pure elements and/or compounds for which analysis of said object is performed, to obtain selected elements; (220) determining the absorption coefficient for the selected pure elements and/or compounds according to the selected energy range; (230) determining the integrated density of the selected pure elements and/or compounds. Additional and alternative embodiments are disclosed and claimed.

Claims

1. A method for determining the composition of an object comprising the following procedures:

irradiating said object with X-ray radiation from an X-ray source from a first irradiation direction;

determining for each spatially resolvable transmission path respective of said first irradiation direction the propagation-absorption of X-ray radiation by said object for at least one selected energy range to yield propagation-absorption information for a respective at least one selected substance; and

determining the integrated density for said at least one selected substance for at least one spatially resolvable transmission path of said first irradiation direction by respectively mapping according to said at least one selected substance the entries of said propagation-absorption dataset with the entries of an absorption-coefficient dataset,

wherein said at least one selected substance and said selected energy range are selected according to at least one substance-selection criterion and at least one energy-selection criterion, respectively, in a manner such that a distinguishable dependency exists between the spectral absorption properties for each atomic number of the at least one selected substance and the selected energy range.

2. The method according to claim 1, wherein said at least one energy-selection criterion defines a lower limit and an upper limit of said selected energy range.

3. The method for identifying the elemental composition of said object according to claim 2, wherein said upper limit is determined according to a threshold defining a maximal percentage of scattering effects with respect to the total mass attenuation effect of said at least one selected substance.

4. The method for identifying the elemental composition of said object according to claim 1, wherein said at least one energy-selection criterion defines that maximal 10-90% of the total mass attenuation coefficient are caused by scattering effect.

5. The method for identifying the elemental composition of said object according to claim 1, wherein a lower limit of said selected energy range is selected according to the lowest energy value at which reliable detection of the photons is ensured.

6. The method for identifying the elemental composition of said object according to claim 5, wherein said at least one energy-selection criterion furthermore defines that maximal 10-90% of the total mass attenuation coefficient are caused by scattering effect.

7. The method for identifying the elemental composition of said object according to claim 1, wherein said at least one energy-selection criterion defines the exclusion of irradiation energy of at least one of the following:

energy where fluorescence peaks; and

energy where electron excitation peaks occur.

8. The method for identifying the elemental composition of said object according to claim 7, wherein said at least one energy-selection criterion additionally defines that maximal 10-90% of the total mass attenuation coefficient are caused by scattering effect.

9. The method for identifying the elemental composition of said object according to claim 6, wherein the lower limit of said selected energy range is furthermore selected according to the lowest energy value at which reliable detection of the photons is ensured.

10. The method for identifying the elemental composition of said object according to claim 9, wherein said at least one energy-selection criterion additionally defines that maximal 10-90% of the total mass attenuation coefficient are caused by scattering effect.

11. The method for identifying the elemental composition of said object according to claim 1, wherein said at least one energy-selection criterion defines the exclusion of irradiation energy affected in terms of emitted energy by substances employed by a composition determining system used for performing the procedures of claim 1.

12. The method for identifying the elemental composition of said object according to claim 1, wherein said at least one substance-selection criterion defines that the value of exponent a(Z) in E^a(Z)·

Z^b(E) is unique for all occurring atomic numbers Z of the elements of the at least one selected substance.

13. The method for identifying the elemental composition of said object according to claim 1, wherein said at least one substance-selection criterion defines a minimum difference |a(Z₁)−

a(Z₂)|, wherein Z₁ and Z₂ are any one of two different atomic numbers.

14. The method for identifying the elemental composition of said object according to claim 9, wherein said at least one substance-selection criterion furthermore defines a minimum difference of |a(Z₁)−

a(Z₂)|, wherein Z₁ and Z₂ are any one of two different atomic numbers of the elements of the at least one selected substance.

15. The method for identifying the elemental composition of said object according to claim 14, wherein said minimum difference is in the range of 0.001 to 0.010.

16. The method for determining the composition of an object according to claim 1 additionally comprising the step of determining for at least one spatially resolvable position in said object the local density of said at least one selected substance.

17. The method for determining the composition of an object according to claim 1, comprising performing the procedures for a plurality of different irradiation directions with respect to said object.

18. The method for identifying the elemental composition of an object according to claim 1 comprising the following procedure prior to irradiating said object with X-ray radiation from an X-ray source from a first irradiation direction:

selecting, according to said at least one substance-selection criterion, at least one substance for which analysis of said object is performed to obtain said at least one selected substance;

selecting an energy range of an irradiation energy range according to said at least one energy-selection criteria to obtain a selected energy range; and

determining the absorption coefficient of said at least one selected substance for said at least one selected X-ray energy range.

19. A composition determining system operative to identify the composition of an object said composition determining system comprising:

an X-ray source operative to emit X-rays; and

an X-ray detector that enables determining the propagation-absorption of X-rays by said object for a first irradiation direction;

wherein said X-ray detector is operatively coupled with;

a controller;

a storage device comprising a set of instructions; and

a power supply;

wherein said controller when executing said instructions is at least operative to perform the following procedures based on the determined propagation-absorption;

determining, for at least one selected substance and at least one selected energy range, the integrated density in said object for a transmission path respective of said first irradiation direction,

wherein said at least one selected substance and said selected energy range are selected according to at least one substance-selection criterion and at least one energy-selection criterion, respectively, such that a distinguishable dependency exists between the spectral absorption properties for each atomic number of the at least one selected substance and the selected energy range.

20. The composition determining system operative to identify the composition of an object according to claim 20, wherein said controller is operative to determine for a spatially resolvable position in the object the local density of said at least one selected substance.