Method and Apparatus for Determining Asymmetry in an Image

• US 20080095419A1
• Filed: 09/01/2005
• Published: 04/24/2008
• Est. Priority Date: 09/10/2004
• Status: Active Grant

• Current Assignee: Agency For Science Technology and Research (Government of Singapore)
• Original Assignee: Agency For Science Technology and Research (Government of Singapore)
• Inventors: Nowinski, Wieslaw, Volkau, Ihar
• Granted Patent: US 7,805,001 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: G01R 33/56 Image enhancement or correction, e.g. subtraction or averaging techniques , e.g. improvement of signal-to-noise ratio and resolution
• CPC Class Codes: G01R 33/5608 Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels image data processing or generation, in general G06T
• CPC Class Codes: G06T 2207/10088 Magnetic resonance imaging [MRI]
• CPC Class Codes: G06T 2207/30016 Brain
• CPC Class Codes: G06T 7/0012 Biomedical image inspection
• CPC Class Codes: G06T 7/68 of symmetry

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.

Claims

1. A method for determining asymmetry in an image, the method comprising the steps of:

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;

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.

2. The method according to claim 1, wherein the step of compensating comprises moving of the first histogram along said predetermined axis to align said first and second histograms along said axis to receive minimum distance between histograms.

3. The method according to claim 1, wherein the step of determining a symmetry plane comprises determining the mid-saggital plane of an image of a brain.

5. The method of claim 1, wherein the step of determining if the calculated divergence value is greater than a predetermined threshold, comprises comparing said divergence value with a threshold value of around 0.008125.

6. The method of claim 1, further comprising the step of determining one or more maximum (principal) summands in the calculated divergence value and any tissues to which the summands correspond in the image being studied, the summands being indicative of main contributors to asymmetry between the first and second parts.

7. The method of claim 6, further comprising displaying the principal summands and any corresponding tissues to facilitate the location of the asymmetry.

8. The method of claim 1, wherein any one or more of the method steps may be implemented using software and/or hardware.

9. The method of claim 1, wherein the step of determining a symmetry plane to divide the image into a first part and a second part comprises determining a symmetry plane to divide the image into a first part representative of a first hemisphere of a brain and a second part representative of a second hemisphere of the brain.

10. A method for determining asymmetry in a magnetic resonance image (MRI) comprising the method of claim 1.

11. An apparatus arranged to perform a method for determining asymmetry in an image according to claim 1

23. The method of claim 1, wherein the image is an image of a brain having a left hemisphere and a right hemisphere, and wherein the step of determining a symmetry plane comprises determining a symmetry plane to divide the image into a first part comprising the left hemisphere and a second part comprising the right hemisphere.

4. (canceled)

12. A computer program product comprising:

a computer usable 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.

13. An apparatus for determining asymmetry in an image, the apparatus comprising:

a device for determining a symmetry plane to divide the image into a first part and a second part;

that comprise left and right hemispheres respectively;

a device for determining probability distributions of voxels against intensities for the first part and the second part;

a generator for generating a first histogram of intensities representative of the first part and a second histogram of intensities representative of the second part;

a compensator for compensating for any relative shift along a predetermined axis between the first histogram and the second histogram;

a calculator for calculating a divergence value based on distance between the first and second histograms; and

a device for 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 calculator is arranged to determine probability distributions of intensities for the first part and the second part and to calculate the divergence value J 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.

14. The apparatus according to claim 13, wherein the compensator is arranged to move one or other of the first and second histograms along said predetermined axis to align said first and second histograms along said axis.

15. The apparatus according to claim 13, wherein the device for determining the symmetry plane is arranged to determine the mid-saggital plane of an image of a brain.

17. The apparatus of claim 13, wherein the device for determining if the calculated divergence value is greater than a predetermined threshold is arranged to compare said divergence value with a threshold value of around 0.008125.

18. The apparatus of claim 13, further comprising a device for determining one or more maximum (principal) summands in the calculated divergence value and any tissues to which the summands correspond in the image being studied, the summands being indicative of contributors to asymmetry between the first and second parts.

19. The apparatus of claim 18, further comprising a device for displaying the principal summands and any corresponding tissues to facilitate the location of the asymmetry.

20. The apparatus of claim 13, wherein any one or more of the devices, the generator, the compensator and/or the calculator may be implemented using software and/or hardware.

21. The apparatus of claim 13, wherein any one or more of the devices, the generator, the compensator and/or the calculator may be implemented in a computer.

22. The apparatus of claim 13, wherein the image is an image of a brain having a left hemisphere and a right hemisphere, said first part comprising the left hemisphere and said second part comprising the right hemisphere.

24. A scanner comprising the apparatus of claim 13.

16. (canceled)