Apparatus and method for detection of liquids in computed tomography data

• US 6,026,171 A
• Filed: 02/11/1998
• Issued: 02/15/2000
• Est. Priority Date: 02/11/1998
• Status: Expired due to Term

• Current Assignee: Analogic Corporation
• Original Assignee: Analogic Corporation
• Inventors: Crawford, Carl R., Simanovsky, Sergey, Hiraoglu, Muzaffer, Bechwati, Ibrahim M.
• Primary Examiner(s): Au, Amelia
• Assistant Examiner(s): Dastouri, Mehrdad
• Application Number:
  US09/022,064
• Time in Patent Office: 734 Days
• Field of Search: 382/100, 382/128, 382/131, 382/141, 378/4, 378/57, 378/901, 345/420, 345/421, 345/424, 250/306, 250/363.04, 250/290.04
• US Class Current: 382/100
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02
• CPC Class Codes: G01V 5/226 using tomography
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: G06V 2201/05 Recognition of patterns representing particular kinds of hidden objects, e.g. weapons, explosives, drugs

Abstract

A method and apparatus for detecting objects in computed tomography (CT) data are shown. Specifically, the system can identify objects that contain liquids, if desired. A subregion that encloses an object is defined, and a top surface of the subregion is identified. Volume elements at the surfaces of the object are identified. If a ratio of top surface volume elements to the total number of surface volume elements is determined. If that ratio exceeds a predetermined threshold, then the object can be identified as including a liquid.

Claims

1. A method of detecting liquids represented in computed tomography (CT) data for a region comprising:

identifying a plurality of volume elements in the CT data associated with an object, each volume element being associated with a density value;

defining a subregion that encloses the object, said subregion defining a plurality of subregion surfaces;

identifying surface volume elements of the object that are in proximity to surfaces of the subregion;

identifying a top surface of the subregion, said top surface of the subregion being in proximity to a top surface of the object;

identifying top surface volume elements at the top surface of the object;

generating a count of the number of top surface volume elements at the top surface of the object;

computing a ratio of the count to a parameter related to at least one surface of the subregion; and

labeling the object as including a liquid if the ratio exceeds a predetermined threshold.

2. The method of claim 1 wherein the parameter related to at least one surface of the subregion is indicative of the total number of surface volume elements of the object.

3. The method of claim 1 wherein identifying a top surface of the subregion comprises identifying a horizontal surface of the subregion.

4. The method of claim 3 wherein identifying a top surface of the subregion further comprises analyzing volume elements adjacent to the horizontal surface to determine if the horizontal surface is adjacent to air.

5. The method of claim 1 further comprising classifying the object as a non-threat object if the object is labeled as including a liquid.

6. The method of claim 1 wherein the region includes at least a portion of an interior of a container.

7. The method of claim 6 wherein the container is a piece of baggage.

8. The method of claim 1 further comprising generating a histogram of top-surface volume elements.

9. The method of claim 8 wherein a peak in the histogram of top-surface volume elements is used to determine a number of top-surface volume elements.

10. The method of claim 8 further comprising generating a histogram of bottom-surface volume elements.

11. The method of claim 10 wherein a peak in the histogram of bottom-surface volume elements is used to determine a number of bottom-surface volume elements.

12. The method of claim 10 wherein labeling the object as including a liquid comprises computing a ratio of a number of top-surface volume elements to a number of bottom-surface volume elements.

13. The method of claim 10 wherein labeling the object as including a liquid comprises computing a ratio of a number of top-surface volume elements to an area of the top surface of the subregion.

14. The method of claim 1 wherein the parameter related to at least one surface of the subregion is indicative of the area of the top surface of the subregion.

15. The method of claim 1 wherein the parameter related to at least one surface of the subregion is indicative of the number of bottom surface volume elements of the object.

16. An apparatus for detecting liquids in computed tomography (CT) data for a region comprising:

means for identifying a plurality of volume elements in the CT data associated with an object, each volume element being associated with a density value;

means for defining a subregion that encloses the object, said subregion defining a plurality of subregion surfaces;

means for identifying surface volume elements of the object that are in proximity to surfaces of the subregion;

means for identifying a top surface of the subregion said top surface of the subregion being in proximity to a top surface of the object;

means for identifying top surface volume elements at the top surface of the object;

means for generating a count of the number of top surface volume elements at the top surface of the object;

means for computing a ratio of the count to a parameter related to at least one surface of the subregion; and

means for labeling the object as including a liquid if the ratio exceeds a predetermined threshold.

17. The apparatus of claim 16 wherein the parameter related to at least one surface of the subregion is indicative of the total number of surface volume elements of the object.

18. The apparatus of claim 16 wherein the means for identifying a top surface of the subregion comprises means for identifying a horizontal surface of the subregion.

19. The apparatus of claim 18 wherein the means for identifying a top surface of the subregion further comprises means for analyzing volume elements adjacent to the horizontal surface to determine if the horizontal surface is adjacent to air.

20. The apparatus of claim 16 further comprising means for classifying the object as a non-threat object if the object is labeled as including a liquid.

21. The apparatus of claim 16 wherein the region includes at least a portion of an interior of a container.

22. The apparatus of claim 21 wherein the container is a piece of baggage.

23. The apparatus of claim 16 further comprising means for generating a histogram of top-surface volume elements.

24. The apparatus of claim 23 wherein a peak in the histogram of top-surface volume elements is used to determine a number of top-surface volume elements.

25. The apparatus of claim 23 further comprising means for generating a histogram of bottom-surface volume elements.

26. The apparatus of claim 25 wherein a peak in the histogram of bottom-surface volume elements is used to determine a number of bottom-surface volume elements.

27. The apparatus of claim 25 wherein the means for labeling the object as including a liquid comprises means for computing a ration of a number of top-surface volume elements to a number of bottom-surface volume elements.

28. The method of claim 25 wherein the means for labeling the object as including a liquid comprises means for computing a ratio of a number of top-surface volume elements to an area of the top-surface of the subregion.

29. The apparatus of claim 16 wherein the parameter related to at least one surface of the subregion is indicative of the area of the top surface of the subregion.

30. The apparatus of claim 16 wherein the parameter related to at least one surface of the subregion is indicative of the number of bottom surface volume elements of the object.

31. A computed tomography (CT) scanning system for identifying an object in a region comprising:

means for acquiring CT data for the region;

means for identifying a plurality of volume elements in the CT data associated with an object, each volume element being associated with a density value;

means for defining a subregion that encloses the object, said subregion defining a plurality of subregion surfaces;

means for identifying surface volume elements of the object that are in proximity to surfaces of the subregion;

means for identifying a top surface of the subregion, said top surface of the subregion being in proximity to a top surface of the object;

means for identifying top surface volume elements at the top surface of the object;

means for generating a count of the number of top surface volume elements at the top surface of the object;

means for computing a ratio of the count to a parameter related to at least one surface of the subregion; and

means for labeling the object as including a liquid if the ratio exceeds a predetermined threshold.

32. The CT scanning system of claim 31 wherein the parameter related to at least one surface of the subregion is indicative of the total number of surface volume elements of the object.

33. The CT scanning system of claim 31 wherein the means for identifying a top surface of the subregion comprises means for identifying a horizontal surface of the subregion.

34. The CT scanning system of claim 33 wherein the means for identifying a top surface of the subregion further comprises means for analyzing volume elements adjacent to the horizontal surface to determine if the horizontal surface is adjacent to air.

35. The CT scanning system of claim 31 further comprising means for classifying the object as a non-threat object if the object is labeled as including a liquid.

36. The CT scanning system of claim 31 wherein the region includes at least a portion of an interior of a container.

37. The CT scanning system of claim 36 wherein the container is a piece of baggage.

38. The CT-scanning system of claim 31 further comprising means for generating a histogram of top-surface volume elements.

39. The CT scanning system of claim 38 wherein a peak in the histogram of top-surface volume elements is used to determine a number of top-surface volume elements.

40. The CT scanning system of claim 38 further comprising means for generating a histogram of bottom-surface volume elements.

41. The CT scanning system of claim 40 wherein a peak in the histogram of bottom-surface volume elements is used to determine a number of bottom-surface volume elements.

42. The CT scanning system of claim 40 wherein the means for labeling the object as including a liquid comprises means for computing a ratio of a number of top-surface volume elements to a number of bottom-surface volume elements.

43. The CT scanning system of claim 40 wherein the means for labeling the object as including a liquid comprises means for computing a ratio of a number of top-surface volume elements to an area of the top surface of the subregion.

44. The CT scanning system of claim 31 wherein the parameter related to at least one surface of the subregion is indicative of the area of the top surface of the subregion.

45. The CT scanning system of claim 31 wherein the parameter related to at least one surface of the subregion is indicative of the number of bottom surface volume elements of the object.