Target density imaging using discrete photon counting to produce high-resolution radiographic images

• US 7,166,844 B1
• Filed: 06/01/2004
• Issued: 01/23/2007
• Est. Priority Date: 06/01/2004
• Status: Expired due to Fees

• Current Assignee: Science Applications International Corporation
• Original Assignee: Science Applications International Corporation
• Inventors: Cardone, Frank H., Gormley, Jerome E., Camacho, Hector
• Primary Examiner(s): Porta; David
• Assistant Examiner(s): WEBB, CHRISTOPHER G
• Application Number:
  US10/856,942
• Time in Patent Office: 966 Days
• Field of Search: 250/358.1
• US Class Current: 250/358.1
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays

Abstract

The present invention relates to a system and method for using discrete photon counting to produce transmission radiographic images of a target object with improved spatial resolution and high system sensitivity. The system comprises a radiation source for directing photons at a target object and a detector array for receiving photons passing through the target in order to provide an image of the target density. The detector array is configured to enhance spatial resolution and maintain high system sensitivity. To correct the parallax effect that may be induced by such configuration of the detector array, a process can be computer implemented or program coded to parallax correction.

Claims

1. A system for imaging a target comprising:

a radiation source configured to direct radiation at the target;

a detector array configured to detect at least a portion of the radiation from the radiation source that passes through the target, the detector array includes at least one block detector having a two-dimensional sub-array of discrete detectors, the two-dimensional sub-array of discrete detectors includes;

a plurality of scintillators configured to receive radiation from the radiation source and convert the radiation to light;

at least one photomultiplier tube (PMT) configured to receive the light from the scintillators; and

at least one light guide configured to guide the light from the plurality of scintillators to the at least one PMT, the at least one PMT is configured to detect light from all of the plurality of scintillators in the block detector; and

a first controller configured to receive data relating to the detected radiation and so generate a density image of the target that is corrected for a parallax effect.

2. The system of claim 1, at least one of the discrete detectors includes a scintillation crystal.

3. The system of claim 1, a row of the discrete detectors arranged in a traveling direction of the target in each of the block detectors provides one image pixel of the density image.

4. The system of claim 3, the parallax effect is induced at least by the row of discrete detectors that provides the one image pixel of the density image.

5. The system of claim 1, at least one of the plurality of scintillators has a width of approximately 4 to 8 mm.

6. The system of claim 1, at least one of the plurality of scintillators has a width of approximately 6 mm.

7. The system of claim 1, the two-dimensional sub-array of discrete detectors includes an n×

n array of discrete detectors, with n being a natural number equal to or greater than 2.

8. The system of claim 1, the at least one block detector further includes associated circuitry having an amplifier, an analog-to-digital converter (ADC), a field programmable gate array (FPGA), and a microcontroller, the associated circuitry configured to receive signals from the two-dimensional sub-array of discrete detectors and to generate at least some of the data relating to the detected radiation from the detector array.

9. The system of claim 8, the FPGA is configured to include a look-up table used to identify a location of each of the discrete detectors that detect the radiation from the radiation source.

10. The system of claim 1, the detector array further including:

least one detector module having at least one of the block detectors.

11. The system of claim 10, further including:

a second controller configured to receive from the at least one detector module at least some of the data relating to the detected radiation from the detector array and to pass the at least some data to the first controller.

12. The system of claim 1, the target is selected from the group consisting of:

a closed package, a box, a suitcase, a cargo container, an automobile, a semi-trailer, a tanker truck, and a railroad car.

13. The system of claim 1, the at least one block detector includes sixteen (16) block detectors.

14. The system of claim 1, the target includes a stationary target.

15. The system of claim 1, the target includes a moving target.

16. The system of claim 1, wherein the fist controller includes:

first circuitry configured to receive the data related to the detected radiation;

second circuitry configured to correct the parallax effect; and

a display configured to generate the density image that is corrected for the parallax effect.

17. The system of claim 1, the at least one PMT includes four (4) PMTs, and the at least one light guide includes four (4) light guides.

18. The system of claim 1, further comprising a look-up table for identifying a location of each of the discrete detectors that detect the radiation from the radiation source.

19. A method for imaging a target comprising:

directing radiation at a target;

detecting at least a portion of the radiation that passes through the target, the at least a portion of the radiation is detected by a detector array having at least one block detector, the at least one block detector includes a two-dimensional sub-array of discrete detectors;

receiving data relating to the radiation detected by the detector array;

adjusting for a parallax effect in the density image of the target that results from a configuration of the detector array; and

providing a look-up table to identify a location of each of the discrete detectors that detect the radiation.

20. The method of claim 19, further comprising:

providing one image pixel of the density image of the target from a row of the discrete detectors in the at least one block detector.

21. The method of claim 20, further comprising:

determining the parallax effect as induced from the row of the discrete detectors providing the one image pixel.

22. The method of claim 20, further comprising:

detecting a velocity of the target relative to the detector array;

providing a predetermined resolution of the one image pixel based on the detected velocity.

23. The method of claim 19, the target is selected from the group consisting of:

a closed package, a box, a suitcase, a cargo container, an automobile, semi-trailer, a tanker truck, and a railroad car.

24. The method of claim 19, the target includes a stationary target.

25. The method of claim 19, the target includes a moving target.

26. A system for imaging a target comprising:

a radiation source configured to direct radiation at the target;

a detector array configured to detect at least a portion of the radiation from the radiation source that passes through the target, the detector array includes at least one block detector having a two-dimensional sub-array of discrete detectors;

a first controller configured to receive data relating to the detected radiation and to generate a density image of the target that is corrected for a parallax effect; and

a plurality of scintillators configured to receive radiation from tire radiation source and convert the radiation to light, at least one of the plurality of scintillators has a width of approximately 4 to 8 mm.

27. A system for imaging a target comprising:

a radiation source configured to direct radiation at the target;

a detector array configured to detect at least a portion of the radiation from the radiation source that passes through the target, the detector array includes at least one block detector having a two-dimensional sub-array of discrete detectors;

a first controller configured to receive data relating to the detected radiation and to generate a density image of the target that is corrected for a parallax effect; and

a plurality of scintillators configured to receive radiation from the radiation source and convert the radiation to light, at least one of the plurality of scintillators has a width of approximately 6 mm.

28. A system for imaging a target comprising:

a radiation source configured to direct radiation at the target;

a detector array configured to detect at least a portion of the radiation from the radiation source that passes through the target, the detector array includes at least one block detector having a two-dimensional sub-array of discrete detectors;

a first controller configured to receive data relating to the detected radiation and generate a density image of the target that is corrected for a parallax effect; and

a look-up table for identifying a location of each of the discrete detectors that detect the radiation from the radiation source.

29. A system for imaging a target comprising:

a radiation source configured to direct radiation at the target;

a detector array configured to detect at least a portion of the radiation from the radiation source that passes through the target, the detector array includes at least one block detect or having a two-dimensional sub-array of discrete detectors, the two-dimensional sub-array of discrete detectors includes;

a plurality of scintillators configured to receive radiation from the radiation source and convert the radiation to light;

at least one photomultiplier tube (PMT) configured to receive the light from the scintillators; and

at least one light guide configured to guide the light from the plurality of scintillators to the at least one PMT, the at least one PMT includes four (4) PMTs, and the at least one light guide includes four (4) light guides; and

a first controller configured to receive data relating to the detected radiation and to generate a density image of the target that is corrected for a parallax effect.