Contraband detection systems using a large-angle cone beam CT system

• US 20050276376A1
• Filed: 05/27/2005
• Published: 12/15/2005
• Est. Priority Date: 05/27/2004
• Status: Active Grant

• Current Assignee: L-3 Communications Security and Detection Systems Incorporated
• Original Assignee: L-3 Communications Security & Detection Systems, Inc. (Leidos Holdings, Inc.)
• Inventors: Eilbert, Richard F.
• Granted Patent: US 7,324,625 B2
• Time in Patent Office: Days
• US Class Current: 378/57
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/405 Source units specially adapted to modify characteristics of the beam during the data acquisition process A61B6/4021, A61B6/4035 take precedence
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/482 involving multiple energy 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: G01V 5/224 Multiple energy techniques using one type of radiation, e.g. X-rays of different energies
• CPC Class Codes: G01V 5/226 using tomography

Abstract

A contraband detection system using a cone beam computed tomography scanner. The cone beam scanner allows for rapid acquisition of data for computing three dimensional density maps of objects within items under inspection. Where greater resolution is desired, the image information obtained with the cone beam computed tomography scanner may be combined with higher resolution images formed with a single view scanner. A multi-energy single view scanner may be used to additionally provide information on the effective atomic number of objects contained within items under inspection. Additionally, information obtained with the cone beam computed tomography scanner may be used to increase the accuracy of the computation of the effective atomic number of objects within the item under inspection.

Claims

1. A contraband detection system, comprising:

a) a gantry rotating about an axis and having an opening therethrough;

b) an inspection area within the opening;

c) a radiation source mounted on the gantry, emitting a beam of radiation toward the inspection area, the beam having a divergence along the axis; and

d) a detector array positioned on the gantry, the detector array having a width along the axis sufficient to intersect the beam across a divergence of at least ±

3 degrees.

2. The contraband detection system of claim 1, wherein the detector array has a width sufficient to intersect the beam across a divergence of about ±

5 degrees.

3. The contraband detection system of claim 1, wherein the detector has a width along the axis of in excess of 20 cm.

4. The contraband detection system of claim 1, wherein the detector has a width along the axis of approximately 30 cm.

5. he contraband detection system of claim 1, additionally comprising a reconstructor coupled to the detector array to receive data output by detectors in the array.

6. he contraband detection system of claim 5, wherein the reconstructor processes data at a rate of at least 180 MByte per second.

7. The contraband detection system of claim 6, wherein the reconstructor comprises a plurality of ASICs.

8. The contraband detection system of claim 7, wherein the plurality of ASICs are configured in a plurality of pipelined chains.

9. The contraband detection system of claim 6, wherein the reconstructor comprises a plurality of programmable logic devices.

10. The contraband detection system of claim 9, wherein the plurality of programmable logic devices are configured in a plurality of pipelined chains.

11. The contraband detection system of claim 5, additionally comprising an optical coupling carrying data output by the detectors in the array to the reconstructor.

12. The contraband detection system of claim 1, additionally comprising a conveyor passing through the inspection area.

13. The contraband detection system of claim 1, wherein the gantry rotates about the axis at a rate of at least 1.5 revolutions per second.

14. The contraband detection system of claim 1, additionally comprising a processor coupled to the detector array and adapted to receive output values from detectors in the array and programmed to compute a volumetric representation of an item under inspection.

15. The contraband detection system of claim 14, additionally comprising a dual energy scanner producing projection data representing an item under inspection.

16. The contraband detection system of claim 1, wherein the detector array comprises at least 32 rows of detectors.

17. A method of analyzing an item for the presence of contraband, comprising:

a) forming a projection image of the item with a first resolution using a multi-energy scanner;

b) forming a computed tomography image of the item with a second resolution, less than the first resolution, using a cone beam computed tomography scanner; and

c) forming, based at least on the projection image and the computed tomography image, an image representative of an object within the item, including an indication of an effective atomic number of the object.

18. The method of claim 17 wherein forming a computed tomography image comprises forming an image with a resolution of about 2 mm.

19. The method of claim 17, wherein forming an image representative of an object within the item, comprises delineating the object using density information obtained from the computed tomography image and obtaining effective atomic number from the projection image, corrected based on the delineation of objects.

20. The method of claim 17, wherein forming a computed tomography image comprises forming an image with a detector array spanning approximately 120 degrees of arc.

21. The method of claim 17, wherein the method additionally comprises moving the item along a conveyor having a direction of motion and forming a computed tomography image comprises forming an image with a detector array having a width in the direction of motion of at least 25 cm.

22. The method of claim 21, wherein forming a computed tomography image of the item comprises reconstructing a representation of the item from a helical scan of the item.

23. A method of operating a contraband detection system to inspect an item, comprising:

a) passing the item through the contraband detection system;

b) while the item is passing through the contraband detection system, moving a radiation source and a detector array around the item and about an axis of rotation; and

c) detecting radiation from the source with the detector array, wherein the detector array has an extent of at least 5 degrees along the axis of rotation relative to an apex at the source.

24. The method of claim 23, wherein the detector array has a width in excess of 20 cm along the axis of rotation.

25. The method of claim 23, further comprising reconstructing an image of the item using a reconstruction technique selected from the group consisting of FDK, ASSR and LROI.

26. The method of claim 23, wherein moving the radiation source and the detector array comprises rotating the radiation source and detector array at a rate of at least 2.5 revolutions per second.

27. The method of claim 26, wherein the method additionally comprises transferring data from the detector array to an analysis computer at a rate of at least 150 MB/second.

28. The method of claim 23, wherein the algorithm for reconstruction of the CT image is efficient and exact.