US6076400A
Expired / Lapsed
US
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Apparatus and method for classifying objects in computed tomography data using density dependent mass thresholds
Assignee: Analogic Corp
•
Filing: 1998-02-11
•
Granted: 2000-06-20
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Expires: 2018-02-11
Abstract
Abstract A method and apparatus for detecting objects in computed tomography (CT) data are disclosed. Sheet-shaped objects such as sheet explosives can be detected by analyzing a neighborhood of voxels surrounding a test voxel. If the density of the test voxel is sufficiently different from the mean density of the neighboring voxels, then it is concluded that the test voxel is associated with a sheet object. Sheet objects can also be detected by eroding the CT data so as to eliminate voxels associated with thin objects. Remaining objects are then subtracted from the original data, leaving only thin sheet-shaped objects. Erosion of the data can be performed by identifying a neighborhood of voxels surrounding a voxel of interest. If the number of voxels having densities below a predetermined threshold exceeds a predetermined number, then it is assumed that the test voxel is a surface voxel and is removed from the object. A connectivity process can be applied to voxels to combine them into objects after sheets are detected to prevent sheets from being inadvertently removed from the data by erosion. A dilation function can then be performed on the eroded object to replace surface voxels removed by erosion. A corrected mass using the mean eroded density of the object can be computed and compared to mass thresholds to classify the object as to whether it poses a threat. Multiple mass thresholds can be used, each of which is associated with a particular density range based on the density of an expected threat object. Bulk objects can be detected by a modified morphological connected components labeling (CCL) approach which performs a series of erosion and dilation steps to separate adjacent objects in the data such that they can be individually labeled and analyzed. A merging process can be used to reconnect related items, such as multiple sticks, that were separated during an erosion step. The merging process allows multiple objects that would individually pass as non-threat items to be combined into a single item that is correctly classified as a threat. The system can also identify objects that contain liquids, if desired. The process of the invention can be carried out in multiple stages. The overall system performance, including overall object detection rate and false alarm rate, can be adjusted by adjusting individual object detection rates and/or false alarm rates.
Inventors
- 👤 Ibrahim M. Bechwati
- 👤 Sergey Simanovsky
- 👤 Muzaffer Hiraoglu
- 👤 Carl R. Crawford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 11:14
CPC Classifications
G; G06; G06V; G06V20/00; G06V20/50; G06V20/52; G06V2201/00; G06V2201/05
Claims Analysis
Total Claims: 45
Claim 1
Independent Claim
190 words
A method of classifying an object represented in computed tomography (CT) data for a region comprising: identifying a plurality of volume elements in the CT data each volume element being associated with a density value; for each of a plurality of volume elements, comparing the density value of the volume element to a volume element density range; if the density value of the volume element is within said volume element density range, identifying the volume element as an object volume element; combining a plurality of identified object volume elements into an object; using the density values associated with the combined object volume elements, calculating a density of the object; identifying an object density range which contains the calculated density of the object; selecting an object mass range based on the calculated density of the object wherein the selected object mass range is associated with the object density range; calculating a mass of the object; comparing the mass of the object with the selected object mass range; if the mass of the object is within the selected object mass range, classifying the object as belonging to a predetermined class of objects.
Claim 2
Independent Claim
190 words
A method of classifying an object represented in computed tomography (CT) data for a region comprising: identifying a plurality of volume elements in the CT data each volume element being associated with a density value; for each of a plurality of volume elements, comparing the density value of the volume element to a volume element density range; if the density value of the volume element is within said volume element density range, identifying the volume element as an object volume element; combining a plurality of identified object volume elements into an object; using the density values associated with the combined object volume elements, calculating a density of the object; identifying an object density range which contains the calculated density of the object; selecting an object mass range based on the calculated density of the object wherein the selected object mass range is associated with the object density range; calculating a mass of the object; comparing the mass of the object with the selected object mass range; if the mass of the object is within the selected object mass range, classifying the object as belonging to a predetermined class of objects.
Claim 3
Dependent Claim
17 words
The method of claim 1 wherein the predetermined class of objects is a class of threat objects.
Claim 4
Dependent Claim
16 words
The method of claim 1 wherein the predetermined class of objects is a class of explosives.
Claim 5
Dependent Claim
18 words
The method of claim 1 wherein the object density range includes a density of a known threat material.
Claim 6
Dependent Claim
16 words
The method of claim 1 wherein the object density range includes a density of an explosive.
Claim 7
Dependent Claim
58 words
The method of claim 1 wherein the identified object density range is selected from first and second object density ranges associated with first and second object mass ranges, respectively, and first and second predetermined classes of objects, respectively, such that the object can be classified as belonging to one of the first and second predetermined classes of objects.
Claim 8
Dependent Claim
19 words
The method of claim 6 wherein the second predetermined class of objects is a second class of threat objects.
Claim 9
Dependent Claim
18 words
The method of claim 6 wherein the second predetermined class of objects is a second class of explosives.
Claim 10
Dependent Claim
19 words
The method of claim 6 wherein the second object density range includes a density of a known threat material.
Claim 11
Dependent Claim
17 words
The method of claim 6 wherein the second object density range includes a density of an explosive.
Claim 12
Dependent Claim
16 words
The method of claim 6 wherein the first and second object density ranges do not overlap.
Claim 13
Dependent Claim
12 words
The method of claim 1 wherein the object comprises an explosive material.
Claim 14
Dependent Claim
19 words
The method of claim 1 wherein the region includes at least a portion of an interior of a container.
Claim 15
Dependent Claim
13 words
The method of claim 13 wherein the container is a piece of baggage.
Claim 16
Independent Claim
207 words
An apparatus for classifying an object in computed tomography (CT) data for a region comprising: means for identifying a plurality of volume elements in the CT data each volume element being associated with a density value; means for comparing the density value of each volume element of a plurality of volume elements to a volume element density range; means for identifying the volume element as an object volume element if the density value of the volume element is within said volume element density range; means for combining a plurality of identified object volume elements into an object; means for calculating a mass of the object; means for calculating a density of the object using the density values associated with the combined object volume elements; means for identifying an object density range which contains the calculated density of the object; means for selecting an object mass range based on the calculated density of the object, said selected object mass range being associated with the object density range; means for comparing the mass of the object with the selected object mass range; and means for classifying the object as belonging to a predetermined class of objects if the mass of the object is within the selected object mass range.
Claim 17
Independent Claim
207 words
An apparatus for classifying an object in computed tomography (CT) data for a region comprising: means for identifying a plurality of volume elements in the CT data each volume element being associated with a density value; means for comparing the density value of each volume element of a plurality of volume elements to a volume element density range; means for identifying the volume element as an object volume element if the density value of the volume element is within said volume element density range; means for combining a plurality of identified object volume elements into an object; means for calculating a mass of the object; means for calculating a density of the object using the density values associated with the combined object volume elements; means for identifying an object density range which contains the calculated density of the object; means for selecting an object mass range based on the calculated density of the object, said selected object mass range being associated with the object density range; means for comparing the mass of the object with the selected object mass range; and means for classifying the object as belonging to a predetermined class of objects if the mass of the object is within the selected object mass range.
Claim 18
Dependent Claim
17 words
The apparatus of claim 15 wherein the predetermined class of objects is a class of threat objects.
Claim 19
Dependent Claim
15 words
The apparatus of claim 15 wherein the predetermined class of objects is class of explosives.
Claim 20
Dependent Claim
18 words
The apparatus of claim 15 wherein the object density range includes a density of a known threat material.
Claim 21
Dependent Claim
16 words
The apparatus of claim 15 wherein the object density range includes a density of an explosive.
Claim 22
Dependent Claim
58 words
The apparatus of claim 15 wherein the identified object density range is selected from first and second object density ranges associated with first and second object mass ranges, respectively, and first and second predetermined classes of objects, respectively, such that the object can be classified as belonging to one of the first and second predetermined classes of objects.
Claim 23
Dependent Claim
16 words
The apparatus of claim 20 wherein the first and second object density ranges do not overlap.
Claim 24
Dependent Claim
18 words
The apparatus of claim 20 wherein the second predetermined class of objects is a class of threat objects.
Claim 25
Dependent Claim
17 words
The apparatus of claim 20 wherein the second predetermined class of objects is a class of explosives.
Claim 26
Dependent Claim
19 words
The apparatus of claim 20 wherein the second object density range includes a density of a known threat material.
Claim 27
Dependent Claim
17 words
The apparatus of claim 20 wherein the second object density range includes a density of an explosive.
Claim 28
Dependent Claim
12 words
The apparatus of claim 15 wherein the object comprises an explosive material.
Claim 29
Dependent Claim
19 words
The apparatus of claim 15 wherein the region includes at least a portion of an interior of a container.
Claim 30
Dependent Claim
13 words
The apparatus of claim 27 wherein the container is a piece of baggage.
Claim 31
Dependent Claim
214 words
A computed tomography (CT) scanning system for classifying 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, each volume element being associated with a density value; means for comparing the density value of each volume element of a plurality of volume elements to a volume element density range; means for identifying the volume element as an object volume element if the density value of the volume element is within said volume element density range; means for combining a plurality of identified object volume elements into an object; means for calculating a mass of the object; means for calculating a density of the object using the density values associated with the combined object volume elements; means for identifying an object density range which contains the calculated density of the object; means for selecting an object mass range based on the calculated density of the object, said selected object mass range being associated with the object density range; means for comparing the mass of the object with the selected object mass range; and means for classifying the object as belonging to a predetermined class of objects if the mass of the object is within the selected object mass range.
Claim 32
Dependent Claim
214 words
A computed tomography (CT) scanning system for classifying 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, each volume element being associated with a density value; means for comparing the density value of each volume element of a plurality of volume elements to a volume element density range; means for identifying the volume element as an object volume element if the density value of the volume element is within said volume element density range; means for combining a plurality of identified object volume elements into an object; means for calculating a mass of the object; means for calculating a density of the object using the density values associated with the combined object volume elements; means for identifying an object density range which contains the calculated density of the object; means for selecting an object mass range based on the calculated density of the object, said selected object mass range being associated with the object density range; means for comparing the mass of the object with the selected object mass range; and means for classifying the object as belonging to a predetermined class of objects if the mass of the object is within the selected object mass range.
Claim 33
Dependent Claim
14 words
The CT scanning system of claim 29 wherein the object comprises an explosive material.
Claim 34
Dependent Claim
21 words
The CT scanning system of claim 29 wherein the region includes at least a portion of an interior of a container.
Claim 35
Dependent Claim
15 words
The CT scanning system of claim 31 wherein the container is a piece of baggage.
Claim 36
Dependent Claim
19 words
The CT scanning system of claim 29 wherein the predetermined class of objects is a class of threat objects.
Claim 37
Dependent Claim
17 words
The CT scanning system of claim 29 wherein the predetermined class of objects is class of explosives.
Claim 38
Dependent Claim
20 words
The CT scanning system of claim 29 wherein the object density range includes a density of a known threat material.
Claim 39
Dependent Claim
18 words
The CT scanning system of claim 29 wherein the object density range includes a density of an explosive.
Claim 40
Dependent Claim
60 words
The CT scanning system of claim 29 wherein the identified object density range is selected from first and second object density ranges associated with first and second object mass ranges, respectively and first and second predetermined classes of objects, respectively such that the object can be classified as belonging to one of the first and second predetermined classes of objects.
Claim 41
Dependent Claim
18 words
The CT scanning system of claim 37 wherein the first and second object density ranges do not overlap.
Claim 42
Dependent Claim
20 words
The CT scanning system of claim 37 wherein the second predetermined class of objects is a class of threat objects.
Claim 43
Dependent Claim
18 words
The CT scanning system of claim 37 wherein the predetermined class of objects is a class of explosives.
Claim 44
Dependent Claim
21 words
The CT scanning system of claim 37 wherein the second object density range includes a density of a known threat material.
Claim 45
Dependent Claim
19 words
The CT scanning system of claim 37 wherein the second object density range includes a density of an explosive.
References Cited (Backward Citations)
US4064440A
Cited
US4366382B2
Cited
US4366382A
Cited
US4366382B1
Cited
US4511799A
Cited
US4729098A
Cited
US5044002A
Cited
US4835688A
Cited
US4905148A
Cited
US4903202A
Cited
US5022062A
Cited
US5098640A
Cited
US5125015A
Cited
US5835200A
Cited
US5319547A
Cited
US5490218A
Cited
US5345393A
Cited
US5166876A
Cited
US5233300A
Cited
US5206592A
Cited
US5182764A
Cited
US5647018A
Cited
US5528703A
Cited
US5479023A
Cited
US5291402A
Cited
US5638502A
Cited
US5506785A
Cited
US5544283A
Cited
US5337053A
Cited
US5638499A
Cited
US5606517A
Cited
US5712926A
Cited
WO1996013017A1
Cited
US5548694A
Cited
US5600700A
Cited
US5642393A
Cited
US5642394A
Cited
US5699400A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-06-20 | 2003-12-20 | 2004-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-06-20 | 2007-12-20 | 2008-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-06-20 | 2011-12-20 | 2012-06-20 | $7700.00 | Window Closed / Lapsed |