Method and apparatus for transmitting information about a target object between a prescanner and a CT scanner

• US 6,788,761 B2
• Filed: 11/06/2003
• Issued: 09/07/2004
• Est. Priority Date: 02/06/2002
• Status: Expired due to Fees

• Current Assignee: Leidos Security Detection & Automation Incorporated (Leidos Holdings, Inc.)
• Original Assignee: L-3 Communications Security and Detection Systems Corporation Delaware
• Inventors: Eilbert, Richard F., Shi, Shunghe, Bijjani, Richard R.
• Primary Examiner(s): Church, Craig E.
• Assistant Examiner(s): Kiknadze, Irakli
• Application Number:
  US10/702,362
• Publication Number:
  US 20040101102A1
• Time in Patent Office: 306 Days
• Field of Search: 378/57, 378/4, 378/19, 378/54, 378/53, 378/92, 378/5, 378/98.9, 378/98.11, 382/131
• US Class Current: 378/57
• CPC Class Codes: G01N 2223/402 mapping distribution of elements
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 2223/421 digitised image, analysed in real time (recognition algorithms)
• 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 5/224 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 method or apparatus for analyzing an object includes an X-ray prescanner that performs a prescan of the object to determine prescan information about the object. Then, a CT scanner performs a CT scan on at least one plane of the object based on the prescan information to determine CT information. In one embodiment, if the CT scan of the object includes or is in the vicinity of metal, then metal artifact correction of a constructed image from the CT scan is performed based on the prescan information. In another embodiment, a processor analyzes the CT information and the prescan information to determine whether to update the prescan information based on the CT information.

Claims

1. A method of screening items to detect target objects therein, comprising:

a) passing X-rays through an item from a plurality of different angles and with a plurality of energy levels;

b) detecting X-rays that have been attenuated by passing through the item to produce detected values representative of the attenuation of the X-rays by the item;

c) analyzing the detected values to produce a first representation of objects within the item, the objects in the first representation being based at least in part on a ratio of attenuation of x-rays having different energies;

d) performing a computed tomographic reconstruction of at least a portion of the detected values to produce a second representation of one or more objects within the item;

e) forming a third representation of objects in the item by combining the first and second representations, and

f) wherein forming the third representation includes altering the first representation by changing the estimate of the atomic number of an object based on the second representation of objects.

2. The method of claim 1 wherein the first representation includes as objects areas within a scan of an item having similar atomic number.

3. The method of claim 1 wherein the first representation represents as objects areas within an item of similar atomic number and mass.

4. A method of screening items to detect target objects therein, comprising:

a) passing X-rays through an item from a plurality of different angles and with a plurality of energy levels;

b) detecting X-rays that have been attenuated by passing through the item to produce detected values representative of the attenuation of the X-rays by the item;

c) analyzing the detected values to produce a first representation of objects within the item, the objects in the first representation being based at least in part on a ratio of attention of x-rays haying different energies;

d) performing a computed tomographic reconstruction of at least a portion of the detected values to produce a second representation of one or more object within the item;

e) forming a third representation of objects in the item by combining the first and second representations; and

f) wherein forming the third representation includes altering a representation of an object in the first representation based on the second representation indicating that a plurality of overlapping objects are represented as one object in the first representation.

5. The method of claim 4 wherein the second representation of objects is based on density of objects.

6. The method of claim 4 wherein analyzing the detected values includes forming a two dimensional array of pixels representing the item.

7. The method of claim 6, wherein analyzing the detected values includes identifying regions in the two dimensional array of pixels in which the pixels have similar atomic number and mass.

8. The method of claim 7 wherein regions of similar atomic number are determined from pixels having similar ratios of attenuation of x-rays at two different energies and mass is determined from pixels having similar attenuation of x-rays at the same energy.

9. The method of claim 4 wherein producing the first representation includes assigning an effective atomic number to each object.

10. The method of claim 9 additionally comprising selecting objects of interest based in pair on the effective atomic numbers and wherein performing the computed tomographic reconstruction is altered by the selected objects of interest.

11. The method of claim 10 wherein the computed tomographic reconstruction reconstructs a slice of the item selected to pass through an object of interest.

12. The method of claim 4 wherein the first representation represents objects in a two dimensional coordinate system and the second representation represents objects in a three dimensional coordinate system.

13. The method of claim 4 wherein the first representation is formed from an image of the item from only one view.

14. A method of screening items to detect target objects therein, comprising:

a) passing X-rays through an item from a plurality of different angles and with a plurality of energy levels;

b) detecting X-rays that have been attenuated by passing through the item to produce detected values representative of the attenuation of the X-rays by the item;

c) analyzing the detected values to produce a first representation of objects within the item, the objects in the first representation being based at least in part on a ratio of attenuation of x-rays having different energies;

d) performing a computed tomographic reconstruction of at least a portion of the detected values to produce a second representation of one or more objects within the item;

e) forming a third representation of objects in the item by combining the first and second representations; and

f) wherein forming a third representation includes altering the effective atomic number and mass associated with objects contained in the first representation based on density of objects contained in the second representation.

15. The method of claim 14 additionally comprising automatically identifying a target object based on the third representation.

16. The method of claim 14 wherein the second representation of objects includes a confidence associated with each object.

17. The method of claim 14 wherein analyzing the detected values includes:

i) forming a plurality of pixels and

ii) grouping pixels of similar characteristics and assigning a confidence level to each grouping.

18. The method of claim 17 wherein assigning a confidence level includes assigning a confidence level based on the compactness of the grouping.

19. The method of claim 17 wherein assigning a confidence level includes assigning a confidence level bused on the connectiveness of the grouping.

20. The method of claim 17 wherein assigning a confidence level includes assigning a confidence level based on the gradient of the grouping.

21. The method of claim 17 wherein assigning a confidence level includes assigning a confidence level based on the histogram spread of the grouping.

22. A method of screening items to detect target objects therein, comprising:

a) passing X-rays through an item from a plurality of different angles and with a plurality of energy levels;

b) detecting X-rays that have been attenuated by passing through the item to produce detected values representative of the attenuation of the X-rays by the item;

c) analyzing the detected values to produce a first representation of objects within the item, the first representation being based at least in part on a ratio of attention of x-rays having different energies;

d) performing a computed tomographic reconstruction of at least a portion of the detected values to produce a second representation of one or more objects within the item;

e) indicating an object based at least in part on the first representation and the second representation, wherein the object is indicated when it has an effective atomic number in a predetermined range and a predetermined proximity to another object that has an effective atomic number indicative of metal.

23. The method of claim 22 wherein indicating an object includes indicating the object is a target.

24. The method of claim 22 wherein indicating an object includes indicating an object and a probability the object is a target.

25. The method of claim 22 wherein indicating an object includes comparing values indicative of effective atomic number and physical extent of objects to predetermined information on the effective atomic number and physical extent of target objects.

26. The method of claim 25 wherein the predetermined information includes a histogram of probabilities that an object having a combination of atomic numbers and physical dimensions is a target object.