Dual energy radiation scanning of objects

• US 20070210255A1
• Filed: 02/28/2005
• Published: 09/13/2007
• Est. Priority Date: 03/01/2004
• Status: Active Grant

• Current Assignee: Varex Imaging Corporation
• Original Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Inventors: Bjorkholm, Paul
• Granted Patent: US 8,263,938 B2
• Time in Patent Office: Days
• US Class Current: 250/358.100
• CPC Class Codes: G01N 23/04 and forming images of the material
• CPC Class Codes: G01T 3/00 Measuring neutron radiation G01T5/00 takes precedence
• CPC Class Codes: G01V 5/0041 Multiple energy techniques using one type of radiation, e.g. X-rays of different energies multi-beam applications, e.g. X-rays and neutrons G01V5/0033; spectroscopic applications G01V5/0016
• CPC Class Codes: G01V 5/0069 Measuring induced radiation, e.g. thermal neutron activation analysis investigating or analysing materials by the use of neutrons G01N23/222
• CPC Class Codes: G01V 5/0091 detecting special nuclear material [SNM], e.g. Uranium-235, Uranium-233 or Plutonium-239
• 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 5/234 Measuring induced radiation, e.g. thermal neutron activation analysis
• CPC Class Codes: G01V 5/281 detecting special nuclear material [SNM], e.g. Uranium-235, Uranium-233 or Plutonium-239

Abstract

In one embodiment, a method of examining an object is disclosed comprising scanning an object at first and second radiation energies, detecting radiation at the first and second energies, and calculating a function of the radiation detected at the first and second energies. The function may be calculated for corresponding portions of the object. It is determined whether the object at least potentially comprises high atomic number material having an atomic number greater than a predetermined atomic number based, at least in part, on the function. The function may be a ratio. The function may be compared to a second function, which may be a threshold having a value based, at least in part, on material of the predetermined atomic number. The second function may be the same as the first function.

Claims

1. A method of examining an object, comprising:

scanning at least a portion of an object at first and second radiation energies, wherein the first and second radiation energies are different;

detecting radiation at the first and second radiation energies, after interaction with the at least a portion of the object;

calculating a function of the radiation detected at the first and second energies; and

determining whether the object at least potentially comprises high atomic number material having an atomic number greater than a predetermined atomic number, based, at least in part, on the function.

2. The method of claim 1, wherein the function is a ratio, the method comprising:

calculating the ratio between a function of the radiation detected at the first radiation energy and a function of the radiation detected at the second radiation energy.

3. The method of claim 1, comprising determining whether the object comprises high atomic number material by:

comparing the first function to a second function, wherein the second function is based, at least in part, on the predetermined atomic number.

4. The method of claim 1, wherein the second function defines a threshold, the method comprising:

comparing the first function to the threshold.

5. The method of claim 4, wherein the second function is the same as the first function, the method further comprising:

calculating the second function based, at least in part, on detected radiation after scanning a test material having an atomic number equal to the predetermined atomic number, at the first and second radiation energies.

6. The method of claim 5, wherein the second function is a threshold, the method comprising calculating the threshold by:

calculating a ratio between the radiation detected at the first and second radiations, after interaction with the test material.

7. The method of claim 1, comprising:

calculating the function between the radiation detected at the first and second energies, for corresponding portions of the object.

8. The method of claim 7, wherein corresponding portions of the object overlap by at least half.

9. The method of claim 1, comprising:

detecting radiation at the first and second radiation energies after transmission through the object.

10. A method of examining an object, the method comprising:

scanning a first plurality of portions of an object with a first radiation beam at a first energy;

detecting first radiation after interaction of the first radiation beam with the first plurality of portions;

scanning a second plurality of portions of the object with a second radiation beam at a second energy different than the first energy;

detecting second radiation after interaction of the second radiation beam with the second plurality of portions;

calculating a ratio between functions of the first radiation and the second radiation, for corresponding first and second portions; and

determining whether the contents of the object at least potentially comprises a high atomic number material having an atomic number greater than a predetermined atomic number based, at least in part, on a comparison of each ratio with a threshold.

11. The method of claim 10, further comprising:

calculating the threshold, at least in part, by;

scanning at least a portion of a second object comprising material having an atomic number equal to the predetermined atomic number, with a third radiation beam at the first energy;

detecting third radiation after interaction of the third radiation beam with the at least a portion of the second object;

scanning at least a portion of the second object with a fourth radiation beam at the second energy;

detecting fourth radiation after interaction of the fourth radiation beam with the at least a portion of the second object; and

calculating a second ratio between the functions of the third radiation and the fourth radiation.

12. The method of claim 11, wherein scanning at least a portion of the second object comprises:

scanning at least a portion of a second object comprising a material having an atomic number less than an atomic number of uranium.

13. The method of claim 12, comprising:

scanning at least a portion of a second object comprising a material having an atomic number less than an atomic number of lead.

14. The method of claim 13, comprising:

scanning at least a portion of a second object chosen from the group consisting of iron, copper and nickel.

15. The method of claim 11, further comprising calculating the threshold by:

subtracting a predetermined number of standard deviations from the second ratio, wherein the predetermined number may be an integer or a non-integer.

16. The method of claim 10, wherein:

the first energy is greater than the second energy;

calculating the ratio comprises dividing the first radiation by the second radiation; and

determining that at least one of the plurality of corresponding portions of the object at least potentially comprises a high atomic number material, if the ratio for a respective corresponding portion is less than the threshold.

17. The method of claim 10, further comprising:

selecting a threshold based on radiation detected at at least one of the first radiation and the second radiation.

18. A system for examining an object, comprising:

means for scanning at least a portion of an object at first and second radiation energies, wherein the first and second radiation energies are different;

means for detecting radiation at the first and second radiation energies, after interaction with the object;

means for calculating a function of the radiation detected at the first and second energies; and

means for determining whether the object at least potentially comprises high atomic number material having an atomic number greater than a predetermined atomic number, based, at least in part, on the function.

19. A system for examining an object, the system comprising:

at least one radiation source to scan at least a portion of an object at first and second radiation energies, wherein the first radiation energy is different than the second radiation energy;

at least one detector positioned to detect radiation at the first and second radiation energies, after interaction with the object;

at least one processor coupled to the detector, the at least one processor being programmed to;

calculate a function of the radiation detected at the first and second energies; and

determine whether the object at least potentially comprises high atomic number material having an atomic number greater than a predetermined atomic number based, at least in part, on the function.

20. The system of claim 19, wherein the processor is programmed to:

calculate a ratio between functions of the radiation detected at the first and second energies.

21. The system of claim 19, wherein the processor is programmed to:

compare the first function to a second function, wherein the second function is based, at least in part, on the predetermined atomic number.

22. The system of claim 21, wherein the processor is programmed to calculate the second function based, at least in part, on:

third and fourth radiations detected after scanning a material having an atomic number equal to the predetermined atomic number by the first and second radiation energies, respectively.

23. The system of claim 19, wherein the processor is further programmed to:

calculate the function of the first and second radiations for a plurality of corresponding portions of the object; and

determine whether the object at least potentially compromises high atomic number material having an atomic number greater than a predetermined atomic number based, at least in part on the functions.

24. The system of claim 19, wherein:

the detector is positioned to detect radiation transmitted through the object.

25. A method of examining an object, comprising:

scanning at least a portion of an object at first and second radiation energies, wherein the first and second radiation energies are different;

detecting radiation at the first and second radiation energies, after interaction with the at least a portion of the object;

calculating a function of the radiation detected at the first and second energies;

comparing the function to a threshold value between acceptable and unacceptable material; and

determining whether the object at least potentially comprises unacceptable material, based, at least in part, on the comparison.

26. A method of examining an object, comprising:

scanning at least a portion of an object by a first radiation beam having a first energy, at an angle with respect to the object;

scanning the at least a portion of the object by a second radiation beam having a second energy different than the first energy, at substantially the same angle with respect to the object;

detecting radiation at the first and second radiation energies, after interaction with the at least a portion of the object;

calculating a function of the radiation detected at the first and second energies; and

determining whether the object at least potentially comprises high atomic number material having an atomic number greater than a predetermined atomic number, based, at least in part, on the function.