X-ray inspection system and method

• US 9,113,839 B2
• Filed: 02/22/2011
• Issued: 08/25/2015
• Est. Priority Date: 04/25/2003
• Status: Active Grant

• Current Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Original Assignee: Rapiscan Systems Incorporated (OSI Systems Incorporated)
• Inventors: Morton, Edward James, Baldwin, Francis
• Primary Examiner(s): Artman, Thomas R
• Application Number:
  US13/032,593
• Publication Number:
  US 20110243382A1
• Time in Patent Office: 1,645 Days
• Field of Search: 378/4, 378/5, 378/57, 378/98.9, 382/130, 382/131
• US Class Current: 1/1
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4028 resulting in acquisition of views from substantially different positions, e.g. EBCT
• CPC Class Codes: A61B 6/4085 Cone-beams
• CPC Class Codes: A61B 6/4208 characterised by using a particular type of detector
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/4266 characterised by using a plurality of detector units A61B6/4014 takes precedence
• CPC Class Codes: A61B 6/463 characterised by displaying multiple images or images and diagnostic data on one display
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/5205 involving processing of raw data to produce diagnostic data
• CPC Class Codes: A61B 6/542 involving control of exposure
• CPC Class Codes: G01N 2223/601 density profile
• CPC Class Codes: G01N 2223/639 material in a container
• CPC Class Codes: G01N 23/04 and forming images of the material
• CPC Class Codes: G01N 23/083 the radiation being X-rays
• CPC Class Codes: G01N 23/087 using polyenergetic X-rays
• CPC Class Codes: G01T 1/2008 using a combination of different types of scintillation detectors, e.g. phoswich
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02
• CPC Class Codes: G01V 5/20 Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects

Abstract

The present specification discloses an X-ray system for processing X-ray data to determine an identity of an object under inspection. The X-ray system includes an X-ray source for transmitting X-rays, where the X-rays have a range of energies, through the object, a detector array for detecting the transmitted X-rays, where each detector outputs a signal proportional to an amount of energy deposited at the detector by a detected X-ray, and at least one processor that reconstructs an image from the signal, where each pixel within the image represents an associated mass attenuation coefficient of the object under inspection at a specific point in space and for a specific energy level, fits each of pixel to a function to determine the mass attenuation coefficient of the object under inspection at the point in space; and uses the function to determine the identity of the object under inspection.

Claims

1. A method for processing X-ray data to determine an identity of an object, comprising a material, under inspection, comprising:

transmitting an X-ray beam from an energy source, having energy levels ranging from 10 keV to at least 200 keV, through the object;

detecting said transmitted X-ray beam at a detector array, wherein said detector array is configured to output signals proportional to a spectrum of energy transmitted through the object, wherein said detector array has at least four energy bins and wherein each energy bin comprises a range of energy levels;

reconstructing a plurality of images from said signals, wherein at least one image is reconstructed for each energy bin defined by the detector array and wherein each pixel within each of said plurality of images is associated with a mass attenuation coefficient of the object under inspection at a specific point in space and for said one energy bin; and

for a given pixel, determining a mass attenuation coefficient associated with said pixel in each of the plurality of images to yield a plurality of mass attenuation coefficients, mapping said plurality of mass attenuation coefficients against values of energy associated with each of the plurality of images, generating a graphical curve indicative of the mass attenuation coefficients of the material located at said pixel across said values of energy, acquiring from a database graphical curves indicative of mass attenuation coefficients of known materials across said values of energy, and comparing the generated graphical curve to the acquired graphical curves to determine an identity of said material and of the object.

2. The method of claim 1 wherein determining the identity of the object under inspection is performed by comparing the object'"'"'s linear attenuation coefficient function to data comprising linear attenuation coefficient functions of predefined materials.

3. The method of claim 2 wherein said comparison yields a fit comparing the relationship between mass attenuation coefficients and logarithmic values of energy obtained from the object under inspection to pre-computed material data for known materials.

4. The method of claim 3 wherein, based on said comparison, pixels which are determined to qualify as potential threat materials are highlighted within said image.

5. The method of claim 1 wherein each of said energy levels are substantially mono-energetic energies.

6. The method of claim 5 wherein said mono-energetic energies are within a range of 20 keV to 250 keV.

7. The method of claim 1 wherein each detector in said detector array outputs one of said signals to an amplifier.

8. The method of claim 7 wherein said amplifier amplifies said one of said signals and outputs said amplified signal to a multi-channel analyzer.

9. The method of claim 1 wherein said reconstruction is performed by processing said signals in accordance with at least one of a filtered back projection algorithm or an iterative reconstruction method.

10. The method of claim 1 wherein at least one image is reconstructed for each of the energy levels detected by the detector array.

11. The method of claim 1 wherein said detector array has a resolution of 10 keV and wherein said energy source has a peak electron energy of at least 200 keV.

12. The method of claim 11 wherein a set of at least twenty images are reconstructed.

13. The method of claim 12 wherein said twenty images are derived from signals corresponding to X-rays having energies of at least 10 keV, 20 keV, 30 keV, 40 keV, 50 keV, 60 keV, 70 keV, 80 keV, 90 keV, 100 keV, 110 keV, 120 keV, 130 keV, 140 keV, 150 keV, 160 keV, 170 keV, 180 keV, 190 keV, and 200 keV.

14. The method of claim 1 wherein said energy bins are defined by 50 keV increments.

15. The method of claim 14 wherein, based on said energy bins, four images are reconstructed.

16. An X-ray system for processing X-ray data to determine an identity of an object, comprising material, under inspection, comprising:

an X-ray source for transmitting an X-ray beam, wherein said X-ray beam has a range of energies, through the object;

a detector array for detecting said transmitted X-ray, wherein each detector in said detector array detects at least one energy level in said range of energies and outputs a signal proportional to an amount of energy deposited at said detector by a detected X-ray; and

at least one processor having access to a memory for storing programmatic instructions, wherein when said programmatic instructions are executed, said processor;

i. reconstructs a plurality of images from signals generated by said detector array, wherein each of said plurality of images corresponds to an energy level in said range of energies and wherein each pixel within each of said plurality of images represents an associated mass attenuation coefficient of the object under inspection at a specific point in space and for one energy level in said range of energies; and

ii. for a given point in space, determining a mass attenuation coefficient associated with a pixel at that point in space in each of the plurality of images to yield a plurality of mass attenuation coefficients, mapping said plurality of mass attenuation coefficients against values of energy associated with each of the plurality of images, generating a graphical curve indicative of the mass attenuation coefficients of the material located at said pixel across said values of energy, acquiring from a database graphical curves indicative of mass attenuation coefficients of known materials across said values of energy, and comparing the generated graphical curve to the acquired graphical curves to determine an identity of said material and of said object.

17. The X-ray system of claim 16 wherein determining the identity of the object under inspection is performed by comparing the object'"'"'s linear attenuation coefficient function to data comprising linear attenuation coefficient functions of predefined materials.

18. The X-ray system of claim 17 wherein said comparison yields a fit comparing the relationship between mass attenuation coefficients and logarithmic values of energy obtained from the object under inspection to pre-computed material data for known materials.

19. The X-ray system of claim 18 wherein, based on said comparison, pixels which are determined to qualify as potential threat materials are highlighted within said image.

20. The X-ray system of claim 16 wherein said energy levels within the range of energies are substantially mono-energetic energies.

21. The X-ray system of claim 20 wherein said mono-energetic energies are within a range of 20 keV to 250 keV.

22. The X-ray system of claim 16 further comprising an amplifier for receiving and amplifying the signals proportional to the amount of energy deposited at said detector.

23. The X-ray system of claim 22 wherein said amplifier outputs said amplified signal to a multi-channel analyzer.

24. The X-ray system of claim 16 wherein said detector array has a resolution of 10 keV and wherein said X-ray source has a peak electron energy of at least 200 keV.

25. The X-ray system of claim 24 wherein a set of at least twenty images are reconstructed.

26. The X-ray system of claim 25 wherein said twenty images are derived from signals corresponding to X-rays having energies of at least 10 keV, 20 keV, 30 keV, 40 keV, 50 keV, 60 keV, 70 keV, 80 keV, 90 keV, 100 keV, 110 keV, 120 keV, 130 keV, 140 keV, 150 keV, 160 keV, 170 keV, 180 keV, 190 keV, and 200 keV.

27. The X-ray system of claim 16 wherein the detector array has a plurality of energy bins and wherein at least one image is reconstructed for each energy bin defined by the detector array.

28. The X-ray system of claim 27 wherein said energy bins are defined by 50 keV increments.

29. The X-ray system of claim 28 wherein, based on said energy bins, four images are reconstructed.