Apparatus and method for detecting concealed objects in computed tomography data
First Claim
1. A method of processing computed tomography (CT) data for a region comprising:
- identifying a plurality of volume elements in the CT data for the region, each volume element being associated with a density value;
automatically identifying volume elements in the CT data associated with an object in the region;
automatically identifying at least one subregion in proximity to the object;
automatically calculating at least one property of the subregion; and
processing data for the object based on the calculated property of the subregion.
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Accused Products
Abstract
A method and apparatus for detecting concealed objects in computed tomography data are disclosed. Sheet-shaped objects such as sheet explosives can be detected by a CT scanning system, in particular, a CT baggage scanning system. The invention analyzes CT voxels in a subregion in proximity to the sheet object to determine if the sheet object is concealed in an electronic device or is “sandwiched” within an item such as a book or magazine. To detect electronic concealment, the number of voxels in a subregion that contains the object having a density above a predetermined threshold is counted and the ratio of that number of voxels to the number of object voxels is computed. If the ratio exceeds a threshold, then it is concluded that the object is concealed in electronics. In response, the CT scanning system can alter discrimination parameters to allow the object to be classified as a threat. For “sandwich” concealment, layers on opposite sides of a sheet object are examined. The mean and standard deviation of density values for the voxels are computed. Where the mean density exceeds a predetermined threshold and the standard deviation is below a different threshold, for at least one of the layers, then it is concluded that the sheet object is sandwiched within an innocuous object such as a magazine or a book.
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Citations
54 Claims
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1. A method of processing computed tomography (CT) data for a region comprising:
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identifying a plurality of volume elements in the CT data for the region, each volume element being associated with a density value;
automatically identifying volume elements in the CT data associated with an object in the region;
automatically identifying at least one subregion in proximity to the object;
automatically calculating at least one property of the subregion; and
processing data for the object based on the calculated property of the subregion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
calculating the mean of the density values of volume elements associated with the at least one subregion; and
calculating the standard deviation of the density values of volume elements associated with the at least one subregion.
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17. The method of claim 16 further comprising:
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comparing the calculated mean of the density values to a first threshold;
comparing the calculated standard deviation of the density values to a second threshold; and
processing data for the object based on the comparisons.
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18. The method of claim 17 wherein processing data for the object comprises altering a discrimination parameter used to classify the object as to whether it poses a threat.
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19. The method of claim 17 wherein the object is classified as a threat if the calculated standard deviation is below the second threshold.
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20. The method of claim 19 wherein the object is classified as a threat if the calculated mean is above the first threshold.
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21. The method of claim 1 further comprising counting the number of volume elements in the at least one subregion that have density values within a predetermined range of density values.
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22. The method of claim 21 further comprising:
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comparing the number of volume elements in the at least one subregion that have density values within the predetermined range of density values to the number of volume elements in the object; and
processing data for the object based on the comparison.
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23. The method of claim 22 wherein the predetermined range of density values is selected based on a known density of one or more components of electronic equipment.
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24. The method of claim 22 wherein processing data for the object comprises altering a discrimination parameter used to classify the object as to whether it poses a threat.
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25. The method of claim 24 wherein an altered discrimination parameter is a mass threshold.
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26. The method of claim 22 wherein processing data for the object comprises classifying the object as to whether it poses a threat.
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27. The method of claim 21 further comprising:
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comparing the number of volume elements in the at least one subregion that have density values within the predetermined range of density values to the number of volume elements in the subregion; and
processing data for the object based on the comparison.
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28. The method of claim 27 wherein the predetermined range of density values is selected based on a known density of one or more components of electronic equipment.
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29. The method of claim 27 wherein processing data for the object comprises altering a discrimination parameter used to classify the object as to whether it poses a threat.
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30. The method of claim 29 wherein an altered discrimination parameter is a mass threshold.
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31. The method of claim 27 wherein processing data for the object comprises classifying the object as to whether it poses a threat.
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32. An apparatus for processing computed tomography (CT) data for a region comprising:
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a receiver for receiving the CT data for the region; and
a data processor adapted to;
automatically identify a plurality of volume elements in the CT data for the region, each volume element being associated with a density value;
automatically identify volume elements in the CT data associated with an object in the region;
automatically identify at least one subregion in proximity to the object;
calculate at least one property of the subregion; and
process data for the object based on the calculated property of the subregion. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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Specification