Method and system for detecting threat objects using computed tomography images
First Claim
1. A method of detecting threat objects represented in three-dimensional reconstructed computed tomography data, wherein said three-dimensional tomography data comprises a set of voxels, and wherein a set of pre-computed shape histograms of known threats and a pre-defined threshold are provided, the said method comprises the following steps:
- a. identifying voxels corresponding to a potential threat object;
b. generating a projection from the said voxels corresponding to a potential threat object;
c. obtaining the contour of the boundary of the said potential threat object from the said projection;
d. computing a shape histogram of the said contour;
e. computing the difference measure between the said shape histogram and the said set of pre-computed shape histograms; and
f. declaring that said potential threat object is a threat if said difference measure is less than the said pre-defined threshold.
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Abstract
A method of and system for detecting threat objects represented in 3D CT data uses knowledge of one or more predefined shapes of the threat objects. An object represented by CT data for a region is identified. A two-dimensional projection of the object along a principal axis of the object is generated. A contour of the object boundary in the projection image is computed. A shape histogram is computed from the extracted contour. A difference measure between the extracted shape histogram and a set of pre-computed threat shape histograms is computed. A declaration of a threat object is made if the difference measure is less than a pre-defined threshold.
102 Citations
17 Claims
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1. A method of detecting threat objects represented in three-dimensional reconstructed computed tomography data, wherein said three-dimensional tomography data comprises a set of voxels, and wherein a set of pre-computed shape histograms of known threats and a pre-defined threshold are provided, the said method comprises the following steps:
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a. identifying voxels corresponding to a potential threat object; b. generating a projection from the said voxels corresponding to a potential threat object; c. obtaining the contour of the boundary of the said potential threat object from the said projection; d. computing a shape histogram of the said contour; e. computing the difference measure between the said shape histogram and the said set of pre-computed shape histograms; and f. declaring that said potential threat object is a threat if said difference measure is less than the said pre-defined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A system for detecting threat objects represented in three-dimensional reconstructed computed tomography data, wherein said three-dimensional tomography data comprises a set of voxels, and wherein a set of pre-computed shape histograms of known threats and a pre-defined threshold are provided comprising:
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a. a voxel identification subsystem constructed and arranges so as to identify voxels corresponding to a potential threat object; b. a projection generator constructed and arranged so as to generate a projection from the said voxels corresponding to a potential threat object; c. a contour boundary determinator constructed and arranged so as to obtain the contour of the boundary of the potential threat object from the the projection; d. a histogram determinator constructed and arranged so as to compute a shape histogram of the said contour; e. a difference deteminator constructed and arranged so as to compute the difference measure between the said shape histogram and the said set of pre-computed shape histograms; and f. a potential threat notifier constructed and arranged so as to declare that said potential threat object is a threat if said difference measure is less than the said pre-defined threshold. - View Dependent Claims (16, 17)
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Specification