System and Method for Detecting Tagged Material Using Alpha Matting
First Claim
1. A method for computer-aided object classification, soft segmentation and layer extraction in computed tomographic colonography, said method comprising the steps of:
- providing a contrast enhanced computed tomography (CT) digital image of the colon, said image comprising a plurality of intensities associated with a 3-dimensional (3D) grid of voxels;
finding a foreground region of voxels with an intensity higher than a pre-defined foreground threshold;
creating a 3D trimap of said colon wherein said image is segmented into said foreground region, a background region, and an unknown region between the foreground and background;
starting from said background, extracting successive layers of said unknown region until said foreground region is reached, and classifying each extracted layer as background or foreground; and
generating a foreground matte, a background matte, and an alpha matte, wherein alpha indicates a mixing ration of foreground and background voxels.
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Abstract
A method for computer-aided object classification, soft segmentation and layer extraction in computed tomographic colonography includes providing a contrast enhanced computed tomography (CT) digital image of the colon, finding a foreground region of voxels with an intensity higher than a pre-defined foreground threshold, creating a 3D trimap of the colon where the image is segmented into the foreground region, a background region, and an unknown region between the foreground and background, starting from the background, extracting successive layers of the unknown region until the foreground region is reached, and classifying each extracted layer as background or foreground, and generating a foreground matte, a background matte, and an alpha matte, where alpha indicates a mixing ration of foreground and background voxels.
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Citations
23 Claims
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1. A method for computer-aided object classification, soft segmentation and layer extraction in computed tomographic colonography, said method comprising the steps of:
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providing a contrast enhanced computed tomography (CT) digital image of the colon, said image comprising a plurality of intensities associated with a 3-dimensional (3D) grid of voxels; finding a foreground region of voxels with an intensity higher than a pre-defined foreground threshold; creating a 3D trimap of said colon wherein said image is segmented into said foreground region, a background region, and an unknown region between the foreground and background; starting from said background, extracting successive layers of said unknown region until said foreground region is reached, and classifying each extracted layer as background or foreground; and generating a foreground matte, a background matte, and an alpha matte, wherein alpha indicates a mixing ration of foreground and background voxels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for computer-aided object classification, soft segmentation and layer extraction in computed tomographic colonography, said method comprising the steps of:
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providing a contrast enhanced computed tomography (CT) digital image of the colon, said image comprising a plurality of intensities associated with a 3-dimensional (3D) grid of voxels; creating a 3D trimap of said colon wherein said image is segmented into a foreground region, a background region, and an unknown region between the foreground and background; forming a 3D sphere about a candidate voxel in said region of unknown type; obtaining from the background region within the sphere a number of air voxels, a number of tissue voxels, their respective distance from the candidate voxel, and their variance; obtaining from the foreground region within the sphere a number of tagged voxels having an intensity above a threshold for contrast enhancement, their respective distance from the candidate, and their variance; weighting the intensity of each tissue voxel by its distance from said candidate voxel; weighting the intensity of each air voxel by its distance from said candidate voxel; weighting the intensity of each foreground voxel by its distance from said candidate voxel; and calculating a mixing ratio of foreground and background voxels a from
C=α
F+∫
Ω
(air)Hair(1−
α
(i))Bair(i)+∫
Ω
(tissue)Htissue(1−
α
(i))Btissue(i),wherein C is the intensity of said candidate voxel, Bair is a background air intensity, Btissue is a background tissue intensity, F is a foreground intensity, Ω
is a region of integration in either air voxels or tissue voxels, i represents a voxel in the region of integration, and H is the Heaviside function having a value of 1 inside the region of integration.- View Dependent Claims (12, 13, 15, 16)
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14. A program storage device readable by a computer, tangibly embodying a program of instructions executable by the computer to perform the method steps for computer-aided object classification, soft segmentation and layer extraction in computed tomographic colonography, said method comprising the steps of:
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providing a contrast enhanced computed tomography ((CT) digital image of the colon, said image comprising a plurality of intensities associated with a 3-dimensional (3D) grid of voxels; finding a foreground region of voxels with an intensity higher than a pre-defined foreground threshold; creating a 3D trimap of said colon wherein said image is segmented into said foreground region, a background region, and an unknown region between the foreground and background; starting from said background, extracting successive layers of said unknown region until said foreground region is reached, and classifying each extracted layer as background or foreground; and generating a foreground matte, a background matte, and an alpha matte, wherein alpha indicates a mixing ration of foreground and background voxels. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification