Computed tomography scanning target detection using target surface normals
First Claim
1. A method of detecting a target object in CT image data of an object in three-dimensional image space comprising:
- at a plurality of points along a surface of the object, computing a normal line normal to the surface of the object and extending into the object;
at a plurality of points along each normal line into the object, determining a density of the object from the CT image data; and
using the densities along each normal line, generating an indication of a thickness associated with the object at each normal line.
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Accused Products
Abstract
A method and apparatus for performing CT scans of baggage being carried or loaded onto commercial aircraft are described. The CT baggage scanner of the invention includes numerous features which provide the system with high baggage throughput on the order of seven hundred bags per hour as well as improved image quality and accurate target detection. In one aspect, the scanner includes an adaptive image reconstruction window which identifies data collected from the field of view that are not related to the baggage being scanned. These unrelated data are excluded from the image reconstruction process, resulting in greatly reduced reconstruction time and increased baggage throughput. The invention also includes the capability of performing calibration "air scans" with objects such as the system conveyor in the field of view. Data gathered during the calibration scan are applied to a threshold, and data exceeding the threshold are assumed to be from X-rays that are unobstructed by objects in the field of view and are therefore used to perform the air calibration. The baggage scanner can also analyze scan data to identify shapes of objects, particularly, objects formed in the shape of a sheet. This greatly improves the ability of the system to detect sheet explosives. The system also compensates for detector dark currents and provides dark current offsets which can be dependent upon detector temperature.
147 Citations
20 Claims
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1. A method of detecting a target object in CT image data of an object in three-dimensional image space comprising:
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at a plurality of points along a surface of the object, computing a normal line normal to the surface of the object and extending into the object; at a plurality of points along each normal line into the object, determining a density of the object from the CT image data; and using the densities along each normal line, generating an indication of a thickness associated with the object at each normal line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for detecting a target object in computed tomography (CT) image data of an object in three-dimensional image space comprising:
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means for computing, at a plurality of points along a surface of the object, a normal line normal to the surface of the object and extending into the object; means for determining, at a plurality of points along each normal line into the object, a density of the object from the CT image data; and means for generating an indication of a thickness associated with the object at each normal line using the densities along each normal line. - View Dependent Claims (12, 13, 14, 15)
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16. A computed tomography (CT) system capable of detecting a target object in CT image data of an object in three-dimensional image space comprising:
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means for computing, at a plurality of points along a surface of the object, a normal line normal to the surface of the object and extending into the object; means for determining, at a plurality of points along each normal line into the object, a density of the object from the CT image data; and means for generating an indication of a thickness associated with the object at each normal line using the densities along each normal line. - View Dependent Claims (17, 18, 19, 20)
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Specification