Method for inspecting object using multi-energy radiations and apparatus thereof

• US 7,580,505 B2
• Filed: 12/29/2006
• Issued: 08/25/2009
• Est. Priority Date: 12/31/2005
• Status: Active Grant

• Current Assignee: Nuctech Company Limited (Tsinghua Tongfang Co., Ltd.), Tsinghua University
• Original Assignee: Nuctech Company Limited (Tsinghua Tongfang Co., Ltd.), Tsinghua University
• Inventors: Li, Qinghua, Kang, Ning, Li, Jianmin, Peng, Hua, Liu, Yinong, Li, Yuanjing, Zhang, Li, Li, Junli, Cheng, Jianping, Liu, Yaohong, Chen, Zhiqiang, Wang, Liming, Xie, Yali, Tang, Chuanxiang, Chen, Huaibi, Hu, Haifeng, Kang, Kejun, Wang, Xuewu, Zhong, Huaqiang
• Primary Examiner(s): THOMAS, COURTNEY D
• Application Number:
  US11/647,558
• Publication Number:
  US 20070183568A1
• Time in Patent Office: 970 Days
• Field of Search: 378/5, 378 51- 57, 378/98.9, 378/98.11, 378/98.12
• US Class Current: 378/57
• 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 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

Abstract

The present invention discloses a method for inspecting an object using multi-energy radiations and an apparatus thereof. The method comprises the steps of: causing multi-energy radiations to interact with an object under inspection; detecting and recording detection values after an interaction between the multi-energy radiations and the object under inspection; substituting a portion of the detection values into a predetermined calibration function to obtain information comprising primary material attribute; and determining further material attributes of the object by applying a set of functions suitable for a energy band corresponding to the information. The present invention is applicable to the large container cargo inspection without opening containers at customs, ports and airports.

Claims

1. A method for inspecting an object using multi-energy radiations comprising the steps of:

causing multi-energy radiations to interact with an object under inspection;

detecting and recording detection values after the interaction between the multi-energy radiations and the object under inspection;

substituting a portion of the detection values into a predetermined calibration function to obtain information including primary material attribute; and

determining further material attributes of the object by applying a set of functions for an energy band corresponding to the information.

2. The method of claim 1, wherein the information further includes mass thickness information of the object.

3. The method of claim 1, wherein the calibration function is a fitting function of the detection values obtained after the multi-energy radiations interact with a known material.

4. The method of claim 3, wherein a number of multi-energy radiations which are used for fitting the calibration function and interacting with the known material, is equal to or greater than a number of the multi-energy radiations used for interacting with the materials in the object under inspection.

5. The method of claim 1, wherein the multi-energy radiations include radiations having at least three different energy levels or energy spectra.

6. The method of claim 3, wherein the multi-energy radiations include radiations having at least three different energy levels or energy spectra.

7. The method of claim 1, wherein each detection value obtained after the interaction with the object is a transmission intensity obtained after the radiations penetrate the object.

8. The method of claim 3, wherein each detection value obtained after the interaction with the object is a transmission intensity obtained after the radiations penetrate the object.

9. The method of claim 1, wherein the energy band is a specific energy band corresponding to certain material, and in the energy band, the detection values as a result of the interaction between the radiations and the materials have a greater difference when compared to detection values for other materials.

10. The method of claim 1, wherein the set of functions includes functions capable of amplifying a distinction between the detected values of different materials.

11. The method of claim 1, wherein the set of functions includes different function processing models used for segmental processing corresponding to objects having different mass thickness.

12. The method of claim 1, wherein the source of the radiations is a radioactive isotope.

13. The method of claim 1, wherein the source of the radiations is an accelerator.

14. The method of claim 1, wherein the source of the radiations is an X-ray machine.

15. A method for inspecting an object using multi-energy radiations comprising the steps of:

causing multi-energy radiations to interact with an object under inspection;

detecting and recording detection values after the interaction between the multi-energy radiations and the object under inspection, and forming images corresponding to the multi-energy radiations;

substituting a part of the detection values into a predetermined calibration function to determine a mass thickness of the object; and

selecting weighting factors for the detection values based on the mass thickness to combine the images so as to obtain more accurate gray-scale image.

16. The method of claim 15, further comprising a step of converting the gray-scale image into corresponding color levels in color image.

17. The method of claim 15, wherein the multi-energy radiations include at least two different energy levels or energy spectra.

18. The method of claim 15, wherein determining the mass thickness is based on actual attenuation of the radiations.

19. The method of claim 15, wherein when selecting weighting factors for the detection values, the smaller the mass thickness is, the smaller the weighting factors for the detection values of high-energy radiations are, and the larger the weighting factors for the detection values of low-energy radiations are;

while the larger the mass thickness is, the smaller the weighting factors for the detection values of low-energy radiations are, and the larger the weighting factors for the detection values of high-energy radiations are.

20. An apparatus for inspecting an object using multi-energy radiations comprising:

a radiation source for generating multi-energy radiations which are caused to interact with an obiect under inspection;

a detector module array adapted to detect simultaneously multi-energy radiations;

a processor connected to the detector module array for processing detection values obtained after the interaction between the multi-energy radiations with the object under inspection, said processor having a calibration function for obtaining material attribute and/or for producing gray-scale images of the object; and

a control system connected to the radiation source for changing operating parameters of the radiation source.

21. The apparatus of claim 20, wherein the multi-energy radiations include radiations having at least three different energy levels or energy spectra.

22. The apparatus of claim 20, wherein the multi-energy radiations include radiations having at least three different energy levels or energy spectra.

23. The apparatus of claim 20, wherein the detector module array is a multi-layered multi-crystal detector compounded of different crystals.

24. The apparatus of claim 23, wherein the different crystals of the detector module array are spaced from each other by filter sheets.

25. The apparatus of claim 21, wherein the radiation source is a radioactive isotope.

26. The apparatus of claim 25, wherein the radiation source is a combination of the radioactive isotopes of different elements, and the multi-energy radiations are generated by making the different radioactive isotopes pass through slots of a collimator in a time series.

27. The apparatus of claim 20, wherein the radiation source is an accelerator capable of emitting radiations having a continuous energy spectrum in which respective energy levels predominate.

28. The apparatus of claim 27, wherein the accelerator includes an energy spectrum modulator for modulating the energy spectrum in front end of the radiation exit.

29. The apparatus of claim 20, wherein the radiation source is an X-ray machine.

30. The apparatus of claim 29, wherein the X-ray machine includes an energy spectrum modulator for modulating the energy spectrum in front end of the radiation exit.

31. The apparatus of claim 28, wherein the energy spectrum modulator has a shape of a wheel, with vanes formed of different modulation materials and rotating around an axis in a time series corresponding to the multi-energy radiations.

32. The apparatus of claim 30, wherein the energy spectrum modulator has a shape of a wheel, with vanes formed of different modulation materials and rotating around an axis in a time series corresponding to the multi-energy radiations.

33. The apparatus of claim 28, wherein the energy spectrum modulator synchronizes the multi-level radiations of the radiation source with signal collection of the detector by transmitting a trigger signal to the control system of the radiation source and a collection signal to a controller of the detector module array.

34. The apparatus of claim 33, wherein the energy spectrum modulator has a shape of a wheel, with vanes formed of different modulation materials and rotating around an axis in a time series corresponding to the multi-energy radiations.

35. The apparatus of claim 33, wherein when receiving the trigger signal, the control system sends immediately to the radiation source signals corresponding to the multi-energy radiations so that the radiation source operates in desirable operating states.

36. The apparatus of claim 20, wherein each detection value of the multi-energy radiations is a transmission intensity obtained after the radiations penetrate through the object under inspection.