System and Method for Automated Alignment of Leg Volumes in Whole-Body Magnetic Resonance Scans

• US 20080108893A1
• Filed: 10/29/2007
• Published: 05/08/2008
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens Corporate Research Incorporated (Siemens AG)
• Inventors: Krishnan, Anantha Raman, Zhang, Li
• Granted Patent: US 8,139,830 B2
• Time in Patent Office: Days
• US Class Current: 600/415
• 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 2207/20068 Projection on vertical or horizontal image axis
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 7/33 using feature-based methods

Abstract

A method and system for automatically aligning multiple MR volumes in whole-body MR scans is disclosed. The method and system are capable of automatic alignment of leg-volumes in whole-body MR scans that is insensitive to leg movement. In order to align upper and lower MR volumes, an automatic determination may be made that a junction between the upper and lower MR volumes is in a leg region. The lower MR volume is then divided into left and right regions, and each of the left and right regions are independently aligned with the upper MR volume. One of the left and right regions is then adjusted with respect to the other one to compensate for shifting of the legs with respect to each other.

Claims

1. A method for aligning upper and lower MR volumes, comprising:

dividing said lower MR volume into left and right regions;

independently aligning each of said left and right regions with said upper MR volume; and

adjusting one of said left and right regions with respect to the other one of said left and right regions.

2. The method of claim 1, further comprising:

displaying a composite MR image generated by said aligning and adjusting steps.

3. The method of claim 1, further comprising:

determining whether a junction between said upper and lower MR volumes is in a leg region prior to said step of dividing said lower MR volume into left and right regions.

4. The method of claim 3, wherein said step of determining whether a junction between said upper and lower MR volumes is in a leg region comprises:

(a) determining whether said junction is in a leg region based on a 1D projection profile of an upper portion of said lower MR volume; and

(b) if it is determined that said junction is in a leg region in step (a), determining whether said junction is in a leg region based on coil information associated with said lower MR volume.

5. The method of claim 4, wherein step (a) comprises:

generating said 1D projection profile by projecting said upper portion of said lower MR volume to a width direction;

calculating at least one feature point metric based on said 1D projection profile;

comparing said at least one feature point metric to a corresponding at least one threshold;

if said at least one feature point value satisfies said corresponding at least one threshold, determining that said junction is in a leg region; and

if said at least one feature point value does not satisfy said corresponding at least one threshold, determining that said junction is not in a leg region.

6. The method of claim 5, wherein said step of calculating at least one feature point metric based on said 1D projection profile comprises:

detecting first and second feature points in said 1D projection profile as maximums having a highest magnitude in left and right halves of said 1D projection profile, respectively;

detecting a minimum point in said 1D projection profile with a lowest magnitude between said first and second feature points;

calculating a first metric as a ratio of the magnitude of the minimum point to a mean of the magnitudes of the first and second feature points; and

calculating a second metric as a ratio of a difference between the magnitudes of the first and second feature points to the mean of the magnitudes of the first and second feature points.

7. The method of claim 4, wherein said lower MR volume is stored in a DICOM format, and step (b) comprises:

extracting said coil information associated with said lower MR volume from a DICOM header of said lower MR volume;

comparing a number of peripheral angio (PA) coils in said coil information with a number of non-PA coils is said coil information;

if the number of PA coils is greater than the number of non-PA coils, determining that said junction is in a leg region; and

if the number of PA coils is not greater than the number of non-PA coils, determining that said junction is not in a leg region.

8. The method of claim 1, wherein a junction of said upper and lower MR volumes is in a leg region.

9. The method of claim 8, wherein said step of adjusting one of said left and right regions with respect to the other one of said left and right regions comprises:

compensating for shifts between left and right legs in said upper and lower MR volumes.

10. The method of claim 1, wherein said step of independently aligning each of said left and right regions with said upper MR volume comprises:

calculating alignment parameters for said left region based on correlation of features between said left region and said upper MR volume; and

calculating alignment parameters for said right region based on correlation of features between said right region and said upper MR volume.

11. The method of claim 10, wherein said step of adjusting one of said left and right regions with respect to the other one of said left and right regions comprises:

adjusting the alignment parameters of said one of said left and right regions by subtracting the alignment parameters of said other one of said left and right regions.

13. The apparatus of claim 1, further comprising:

means for determining whether a junction between said upper and lower MR volumes is in a leg region.

14. The apparatus of claim 13, wherein said means for determining whether a junction between said upper and lower MR volumes is in a leg region comprises:

means for determining whether said junction is in a leg region based on a 1D projection profile of an upper portion of said lower MR volume; and

means for determining whether said junction is in a leg region based on coil information associated with said lower MR volume.

15. The apparatus of claim 14, wherein said means for determining whether said junction is in a leg region based on a 1D projection profile of an upper portion of said lower MR volume comprises:

means for generating said 1D projection profile by projecting said upper portion of said lower MR volume to a width direction;

means for calculating at least one feature point metric based on said 1D projection profile; and

means for comparing said at least one feature point metric to a corresponding at least one threshold.

16. The apparatus of claim 14, wherein said lower MR volume is stored in a DICOM format, and said means for determining whether said junction is in a leg region based on coil information associated with said lower MR volume comprises:

means for extracting said coil information associated with said lower MR volume from a DICOM header of said lower MR volume; and

means for comparing a number of peripheral angio (PA) coils in said coil information with a number of non-PA coils is said coil information.

12. An apparatus for aligning upper and lower MR volumes, comprising:

means for dividing said lower MR volume into left and right regions;

means for independently aligning each of said left and right regions with said upper MR volume; and

means for adjusting one of said left and right regions with respect to the other one of said left and right regions.

17. The apparatus of claim 12, wherein said means for independently aligning each of said left and right regions with said upper MR volume comprises:

means for calculating alignment parameters for said left region based on correlation of features between said left region and said upper MR volume; and

means for calculating alignment parameters for said right region based on correlation of features between said right region and said upper MR volume.

18. The apparatus of claim 17, wherein said means for adjusting one of said left and right regions with respect to the other one of said left and right regions comprises:

means for adjusting the alignment parameters of said one of said left and right regions by subtracting the alignment parameters of said other one of said left and right regions.

19. A computer readable medium encoded with computer executable instructions for aligning upper and lower MR volumes, the computer executable instructions defining steps comprising:

dividing said lower MR volume into left and right regions;

independently aligning each of said left and right regions with said upper MR volume; and

adjusting one of said left and right regions with respect to the other one of said left and right regions.

20. The computer readable medium of claim 19, further comprising computer executable instructions defining the step of:

determining whether a junction between said upper and lower MR volumes is in a leg region prior to said step of dividing said lower MR volume into left and right regions.

21. The computer readable medium of claim 20, wherein the computer executable instructions defining the step of determining whether a junction between said upper and lower MR volumes is in a leg region comprise computer executable instructions defining the steps of:

(a) determining whether said junction is in a leg region based on a 1D projection profile of an upper portion of said lower MR volume; and

(b) if it is determined that said junction is in a leg region in step (a), determining whether said junction is in a leg region based on coil information associated with said lower MR volume.

22. The computer readable medium of claim 21, wherein the computer executable instructions defining step (a) comprise computer executable instructions defining the steps of:

generating said 1D projection profile by projecting said upper portion of said lower MR volume to a width direction;

calculating at least one feature point metric based on said 1D projection profile;

comparing said at least one feature point metric to a corresponding at least one threshold;

if said at least one feature point value satisfies said corresponding at least one threshold, determining that said junction is in a leg region; and

if said at least one feature point value does not satisfy said corresponding at least one threshold, determining that said junction is not in a leg region.

23. The computer readable medium of claim 22, wherein the computer executable instructions defining the step of calculating at least one feature point metric based on said 1D projection profile comprise computer executable instructions defining the steps of:

detecting first and second feature points in said 1D projection profile as maximums having a highest magnitude in left and right halves of said 1D projection profile, respectively;

detecting a minimum point in said 1D projection profile with a lowest magnitude between said first and second feature points;

calculating a first metric as a ratio of the magnitude of the minimum point to a mean of the magnitudes of the first and second feature points; and

calculating a second metric as a ratio of a difference between the magnitudes of the first and second feature points to the mean of the magnitudes of the first and second feature points.

24. The computer readable medium of claim 21, wherein said lower MR volume is stored in a DICOM format, and the computer executable instructions defining step (b) comprise computer executable instructions defining the steps of:

extracting said coil information associated with said lower MR volume from a DICOM header said lower MR volume;

comparing a number of peripheral angio (PA) coils in said coil information with a number of non-PA coils is said coil information;

if the number of PA coils is greater than the number of non-PA coils, determining that said junction is in a leg region; and

if the number of PA coils is not greater than the number of non-PA coils, determining that said junction is not in a leg region.

25. The computer readable medium of claim 19, wherein:

the computer executable instructions defining the step of independently aligning each of said left and right regions with said upper MR volume comprise computer executable instructions defining the steps of;

calculating alignment parameters for said left region based of correlation of features between said left region and said upper MR volume, and

calculating alignment parameters for said right region based of correlation of features between said right region and said upper MR volume; and

the computer program instructions defining the step of adjusting one of said left and right regions with respect to the other one of said left and right regions comprise computer program instructions defining the step of;

adjusting the alignment parameters of said one of said left and right regions by subtracting the alignment parameters of said other one of said left and right regions.