Method and apparatus for determining asymmetry in an image
First Claim
1. A computerized method for determining asymmetry in a medical image, the method comprising the steps of:
- receiving the medical image;
determining a symmetry plane to divide the image into a first part and a second part, that comprise left and right hemispheres respectively;
determining probability distributions of voxels against intensities for the first part and the second part;
generating a first histogram of intensities representative of the first part and storing the first histogram on a computer memory;
generating a second histogram of intensities representative of the second part and storing the second histogram on the computer memory;
compensating for any relative shift along a predetermined axis between the first histogram and the second histogram;
calculating, using a computer processor, a divergence value based on distance between the first and second histograms; and
determining if the calculated divergence value is greater than a predetermined threshold, a divergence of greater than the predetermined threshold being indicative of asymmetry in the medical image and indicative of one or more abnormalities, whereinthe step of calculating, using the computer processor, the divergence value comprises determining probability distributions of intensities for the first part and the second part and calculating the J-divergence value according to the following equation;
J(p,q)=I(p,q)+I(q,p)where I(p/q) and I(q/p) are the Kullback-Leibler'"'"'s divergences for intensity distributions q and p of the first and second parts respectively.
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Abstract
A method for determining asymmetry in an image such as an MR image of a brain comprises determining a symmetry plane to divide the image into a first part and a second part representative of, for example, the hemispheres of the brain. The probability distributions of voxels against intensities are determined for the first and second parts and histograms of intensities representative of the parts are generated. Compensation is made for any relative shift along a predetermined axis between the histograms. A divergence value based on a distance between the first and second histograms is then calculated and it is determined if the calculated divergence value is greater than a predetermined threshold. A divergence of greater than the predetermined threshold is indicative of asymmetry in the image that may be considered as suspicious for abnormality. There is also disclosed an apparatus for determining asymmetry in an image.
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Citations
12 Claims
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1. A computerized method for determining asymmetry in a medical image, the method comprising the steps of:
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receiving the medical image; determining a symmetry plane to divide the image into a first part and a second part, that comprise left and right hemispheres respectively; determining probability distributions of voxels against intensities for the first part and the second part; generating a first histogram of intensities representative of the first part and storing the first histogram on a computer memory; generating a second histogram of intensities representative of the second part and storing the second histogram on the computer memory; compensating for any relative shift along a predetermined axis between the first histogram and the second histogram; calculating, using a computer processor, a divergence value based on distance between the first and second histograms; and determining if the calculated divergence value is greater than a predetermined threshold, a divergence of greater than the predetermined threshold being indicative of asymmetry in the medical image and indicative of one or more abnormalities, wherein the step of calculating, using the computer processor, the divergence value comprises determining probability distributions of intensities for the first part and the second part and calculating the J-divergence value according to the following equation;
J(p,q)=I(p,q)+I(q,p)where I(p/q) and I(q/p) are the Kullback-Leibler'"'"'s divergences for intensity distributions q and p of the first and second parts respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12)
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11. A computer program product comprising:
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a non-transitory computer readable medium having a computer readable code and computer readable system code embodied on said medium for determining a symmetry plane to divide the image into a first part and a second part;
that comprise left and right hemispheres respectively, said computer program product further comprising;computer readable code within said computer usable medium for; determining probability distributions of voxels against intensities for the first part and the second part; generating a first histogram of intensities representative of the first part; generating a second histogram of intensities representative of the second part; compensating for any relative shift along a predetermined axis between the first histogram and the second histogram; calculating a divergence value based on distance between the first and second histograms; and determining if the calculated divergence value is greater than a predetermined threshold, a divergence of greater than the predetermined threshold being indicative of asymmetry in the image and indicative of one or more abnormalities, wherein the step of calculating the divergence value comprises determining probability distributions of intensities for the first part and the second part and calculating the J-divergence value according to the following equation;
J(p,q)=I(p,q)+I(q,p)where I(p/q) and I(q/p) are the Kullback-Leibler'"'"'s divergences for intensity distributions q and p of the first and second parts respectively.
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Specification