Method for obtaining strain from radially-tagged magnetic resonance imaging (MRI)

• US 20080009704A1
• Filed: 06/06/2007
• Published: 01/10/2008
• Est. Priority Date: 06/06/2006
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Nasiraei Moghaddam, Abbas, Gharib, Morteza
• Granted Patent: US 8,073,523 B2
• Time in Patent Office: Days
• US Class Current: 600/410
• CPC Class Codes: G01R 33/56333 Involving spatial modulation of the magnetization within an imaged region, e.g. spatial modulation of magnetization [SPAMM] tagging perfusion imaging based on arterial spin tagging G01R33/56366

Abstract

The present invention relates to a system for obtaining strain corresponding to an object'"'"'s deformation by radially-tagged magnetic resonance imaging (MRI). The system acquires at least a ring-shaped crown region of Fourier domain (k-space) data for at least two sequential images of a radially-tagged object at different phases of deformation of the radially-tagged object. A first image represents a primary state of the radially-tagged object and a second image represents a secondary state of the radially-tagged object. Additionally, the images include radial tag lines. The first and second images are reconstructed as a reconstructed primary-state image and a reconstructed secondary-state image. The images are reconstructed as weighted by circumferential density of the radial tag lines, such that they are “tag line density-weighted” reconstructed images. Circumferential strain of the radially-tagged object is determined by comparing the two images.

Claims

1. A method for obtaining strain corresponding to an object'"'"'s deformation by tagged magnetic resonance imaging (MRI) in a radial direction in which a substantially normal strain element is found in a direction substantially perpendicular to the radial direction for tagging, comprising acts of:

acquiring data of at least one crown region in a spatial frequency domain of an object at a primary state and at least one deformed secondary state;

reconstructing one primary-state image of the primary state and one secondary-state image for each deformed secondary state, where the primary-state image and each secondary-state image are filtered and regionally weighted by a radial tag line density of the object; and

determining the strain in the object in the direction substantially perpendicular to the radial direction for tagging by comparing the primary-state image with secondary-state image.

2. A method as set forth in claim 1, wherein in the act of determining strain, a regional strain is determined for a local region by determining an alteration in intensity of the primary-state image and secondary-state image.

3. A method as set forth in claim 2, wherein when determining regional strain, a tracking algorithm is used to find corresponding regions between the primary-state image and the secondary-state image.

4. A method as set forth in claim 3, wherein in the act of determining strain, the strain is determined by a relative shift of an intensity between the primary-state image and the secondary-state image in the corresponding regions between the primary-state image and the secondary-state image.

5. A method as set forth in claim 1, wherein in the act of determining strain, an average intensity is determined by averaging an entire tagged volume in each of the primary-state and secondary-state images.

6. A method as set forth in claim 5, wherein in the act of determining strain, a global strain is determined for an object by comparing the average intensity of the primary-state image to the average intensity of a secondary-state image.

7. A method as set forth in claim 6, wherein when determining global strain, the strain is calculated for a three-dimensional (3D) volume.

8. A method as set forth in claim 1, wherein in the act of acquiring data, the spatial frequency domain is k-space and the crown region is defined by a lower bound k_min and an upper bound k_max which surrounds the center of the k-space and corresponds to an absolute value of spatial frequency k between k_min and k_max.

9. A method as set forth in claim 8, wherein in the act of acquiring data, the data is k-space data, and wherein in the act of reconstructing the primary-state image and the secondary-state image, the images are reconstructed through filtering of the k-space data between k_min and k_max and their Inverse Fast Fourier Transforms (IFFT).

10. A method as set forth in claim 1, wherein in the act of acquiring data, the object is a heart.

11. A method as set forth in claim 1, further comprising an act of filtering the primary-state image and each secondary-state image using a circular narrow band-pass filter.

12. A method as set forth in claim 1, wherein in the act of determining strain, the strain is calculated in a direction substantially perpendicular to a radial tag of the object.

13. A method as set forth in claim 1, wherein in the act of determining strain, the strain is determined regionally for corresponding regions in each of the primary-state and secondary-state images which are determined by a tracking algorithm for the primary-state and secondary-state images.

14. A method as set forth in claim 1, wherein in the act of acquiring data, the data is acquired of an object that is radially-tagged such that a density of radial tagging is uneven around the object.

15. A data processing system for obtaining strain corresponding to an object'"'"'s deformation by tagged magnetic resonance imaging (MRI) in a radial direction in which a substantially normal strain element is found in a direction substantially perpendicular to the radial direction for tagging, the system being configured to perform operations of:

acquiring data of at least one crown region in a spatial frequency domain of an object at a primary state and at least one deformed secondary state;

reconstructing one primary-state image of the primary state and one secondary-state image for each deformed secondary state, where the primary-state image and each secondary-state image are filtered and regionally weighted by a radial tag line density of the object; and

determining the strain of the object in the direction substantially perpendicular to the radial direction for tagging by comparing the primary-state image with secondary-state image.

16. A data processing system as set forth in claim 15, wherein when performing an operation of determining strain, a regional strain is determined for a local region by determining an alteration in intensity of the primary-state image and secondary-state image.

17. A data processing system as set forth in claim 15, wherein when performing an operation of determining strain, an average intensity is determined by averaging an entire tagged volume in each of the primary-state and secondary-state images, and wherein a global strain is determined for an object by comparing the average intensity of the primary-state image to the average intensity of a secondary-state image.

18. A computer program product for obtaining strain corresponding to an object'"'"'s deformation by tagged magnetic resonance imaging (MRI) in a radial direction in which a substantially normal strain element is found in a direction substantially perpendicular to the radial direction for tagging, the computer program product comprising computer-readable instruction means stored on a computer-readable medium that are executable by a computer for causing the computer to:

acquire data of at least one crown region in a spatial frequency domain of an object at a primary state and at least one deformed secondary state;

reconstruct one primary-state image of the primary state and one secondary-state image for each deformed secondary state, where the primary-state image and each secondary-state image are filtered and regionally weighted by a radial tag line density of the object; and

determine the strain of the object in the direction substantially perpendicular to the radial direction for tagging by comparing the primary-state image with secondary-state image.

19. A computer program product as set forth in claim 18, further comprising instruction means for causing a computer to determine regional strain for a local region of the object by determining an alteration in intensity of the primary-state image and secondary-state image.

20. A computer program product as set forth in claim 18, further comprising instruction means for causing a computer to perform operations of:

determining an average intensity by averaging an entire tagged volume in each of the primary-state and secondary-state images; and

determining a global strain for an object by comparing the average intensity of the primary-state image to the average intensity of a secondary-state image.