Radiation scanning with photon tagging

• US 7,630,474 B2
• Filed: 09/28/2007
• Issued: 12/08/2009
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Varex Imaging Corporation
• Original Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Inventors: Clayton, James E.
• Primary Examiner(s): Glick; Edward J
• Assistant Examiner(s): Sanei; Mona M
• Application Number:
  US11/904,817
• Publication Number:
  US 20090086906A1
• Time in Patent Office: 802 Days
• Field of Search: 378/57, 378/119, 378/140, 378/143
• US Class Current: 378/57
• CPC Class Codes: G01N 2223/639 material in a container
• CPC Class Codes: G01N 23/20083 by using a combination of at least two measurements at least one being a transmission measurement and one a scatter measurement

Abstract

In accordance with an embodiment, a method of examining contents of objects comprises accelerating a plurality of electrons to a predetermined acceleration energy and colliding the accelerated electrons with a target. An object is scanned with the generated X-ray photons. First energies of X-ray photons are determined after scanning and second energies of accelerated electrons are determined after colliding with the target, and correlated. Energies of respective detected X-ray photons prior to scanning are determined based, at least in part, on the second energies of respective correlated accelerated electrons and the predetermined acceleration energy. A potential presence of suspect material is determined based, at least in part, on the first energies of respective X-ray photons after scanning and the third energies of the detected X-ray photons prior to scanning. Systems are also disclosed.

Claims

1. A method of examining contents of objects, the method comprising:

accelerating a plurality of electrons to a predetermined acceleration energy;

colliding the accelerated electrons with a target to cause generation of X-ray photons;

scanning at least a portion of an object with at least some of the X-ray photons;

determining first energies of at least some of the X-ray photons after scanning;

determining second energies of at least some of the accelerated electrons after colliding with the target;

correlating respective first energies of respective X-ray photons after scanning with second energies of respective accelerated electrons after colliding with the target;

determining third energies of respective detected X-ray photons prior to scanning based, at least in part, on the second energies of respective correlated accelerated electrons after colliding with the target and the predetermined acceleration energy; and

determining whether a suspect material is at least potentially present based, at least in part, on the first energies of respective X-ray photons after scanning and the third energies of the detected X-ray photons prior to scanning.

2. The method of claim 1, comprising determining whether the suspect material is at least potentially present by:

determining attenuations of respective detected X-ray photons after scanning based, at least in part, on the first energies of the respective detected X-ray photons prior to scanning and the third energies of the respective detected X-ray photons prior to scanning; and

estimating an average atomic number of materials in the scanned portion of the object based, at least in part, on the attenuations.

3. The method of claim 1, comprising accelerating the electrons to a predetermined acceleration energy within a narrow energy band.

4. The method of claim 1, wherein determining the first energies of respective accelerated electrons comprises:

deflecting at least some of the respective accelerated electrons toward a detector by a magnetic field; and

determining the first energies of the respective accelerated electrons detected by the detector based, at least in part, on a degree of deflection.

5. The method of claim 4, comprising determining the first energies of respective accelerated electrons based, at least in part, on a location where the accelerated electrons strike the detector.

6. The method of claim 4, wherein correlating comprises:

determining first times when the detector detects respective accelerated electrons;

determining second times when respective X-ray photons are detected after scanning; and

correlating respective first and second energies based, at least in part, on respective first and second times.

7. The method of claim 6, further comprising:

determining third times when respective X-ray photons are detected by a second detector, before scanning; and

correlating respective first and second energies based, at least in part, on respective first, second times, and third times.

8. The method of claim 1, further comprising blocking passage of X-ray photons having energies below a predetermined energy level, prior to scanning.

9. The method of claim 1, wherein the object is a cargo container having a thickness of at least four feet (1.2 m), the method comprising:

scanning the cargo container.

10. The method of claim 1, comprising:

accelerating the elections to a predetermined acceleration energy in the MeV range.

11. A system for examining contents of an object, the system comprising:

means for accelerating a plurality of electrons to a predetermined acceleration energy;

means for colliding the accelerated electrons with a target to cause generation of X-ray photons;

means for scanning at least a portion of the object with the X-ray photons;

means for detecting energies of respective X-ray photons after scanning;

means for determining energies of respective accelerated electrons after colliding with the target;

means for correlating respective detected energies of X-ray photons after scanning with determined energies of the respective accelerated electrons after colliding with the target;

means for determining energies of respective detected X-ray photons prior to scanning based, at least in part, on the determined energies of respective correlated accelerated electrons after colliding with the target and the predetermined acceleration energy; and

means for determining whether a suspect material is at least potentially present based, at least in part, on the detected energies of respective X-ray photons after scanning and the determined energies of the respective detected X-ray photons prior to scanning.

12. A system for examining contents of an object, the system comprising:

at least one radiation source, the source comprising;

an accelerator configured to accelerate electrons to a predetermined energy; and

a target, wherein impact of the accelerated electrons with the target causes generation of X-ray photons to scan an object;

at least one first detector positioned to detect energies of at least some of the X-ray photons after scanning;

a magnet configured to generate a magnetic field to deflect the accelerated electrons after impacting the target;

at least one second detector to detect at least some of the deflected electrons; and

at least one processor coupled to the at least one first and second detectors, the at least one processor configured to;

determine first energies of respective X-ray photons detected by the first detector;

determine second energies of respective electrons detected by the second detector, after the respective electrons impact the target;

correlate first energies of respective X-ray photons with respective second energies of respective detected electrons;

determine third energies of the respective detected X-ray photons prior to scanning based, at least in part, on the determined second energies of respective correlated electrons and the predetermined acceleration energy; and

provide an output indicative of the potential presence of suspect material based, at least in part, on the first energies of respective X-ray photons and the third energies of the respective X-ray photons prior to scanning.

13. The system of claim 12, wherein the at least one processor is configured to provide an output by:

generating an image indicative of the potential presence of suspect material based, at least in part, on the first and third energies.

14. The system of claim 12, wherein the at least one processor is configured to:

determine attenuations of X-ray photons based, at least in part, on the first energies of respective X-ray photons and the third energies of the respective X-ray photons prior to scanning; and

determine an average atomic number of materials in the scanned portion of the object based, at least in part, on the attenuations.

15. The system of claim 12, wherein the at least one processor is further configured to:

determine first times when the first detector detects respective X-ray photons; and

determine second times when the second detector detects respective electrons; and

correlate respective first and second energies based, at least in part, on respective first and second times.

16. The system of claim 14, further comprising:

a third detector between the target and a position of the object during scanning, to detect passage of respective X-ray photons;

wherein the at least one processor is further configured to;

determine respective third times of passage of respective X-ray photons; and

correlate respective first and second energies based, at least in part, on respective first, second, and third times.

17. The system of claim 16, wherein the system further comprises:

a filter between the target and third detector, the filter being configured to block passage of photons below a predetermined energy.

18. The system of claim 12, wherein the magnet and the second detector are configured such that second energies of respective electrons are proportional to the location where each respective electron impacts the second detector.

19. The system of claim 12, wherein:

the accelerator is configured to accelerate electrons to a predetermined energy in the MeV range.

20. The system of claim 12, wherein the accelerator is configured to accelerate electrons to a predetermined energy within a narrow energy band.

21. The system of claim 13, configured to examine an object having a thickness of at least four feet (1.2 m).

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

accelerating a plurality of charged particles to a predetermined acceleration energy;

colliding the accelerated charged particles with a target to cause generation of X-ray radiation photons;

scanning at least a portion of an object with at least some of the radiation photons;

determining first energies of respective radiation photons after scanning;

determining functions of the energies of accelerated charged particles after colliding with the target, detected within predetermined time periods;

correlating respective first energies of radiation photons after scanning with respective functions of the energies of the accelerated charged particles after colliding with the target;

determining approximate second energies of respective photons prior to scanning based, at least in part, on the functions of the energies of respective correlated accelerated electrons after colliding with the target and the predetermined acceleration energy; and

providing an output based, at least in part, on the approximate second energies of respective radiation photons prior to scanning and respective first energies of the radiation photons after scanning.

23. The method of claim 22, wherein the function is an average.

24. The method of claim 22, comprising:

determining functions of the energies of the accelerated charged particles after colliding with the target, based, at least in part, on the energies of accelerated charged particles after colliding with the target, detected within time periods from about 2 microseconds to about 10 microseconds long.

25. The method of claim 22, comprising:

determining approximate attenuations of respective photons after scanning based, at least in part, on the first energies of respective radiation photons after scanning and the approximate second energies of respective radiation photons prior to scanning; and

providing an output based, at least in part, on the approximate attenuations.