System and Method for Magnetic Resonance Imaging Using Three-Dimensional, Distributed, Non-Cartesian Sampling Trajectories

• US 20150051479A1
• Filed: 03/27/2013
• Published: 02/19/2015
• Est. Priority Date: 04/11/2012
• Status: Active Grant

• Current Assignee: Dignity Health (CommonSpirit Health (Illinois))
• Original Assignee: Dignity Health (CommonSpirit Health (Illinois))
• Inventors: Pipe, James G.
• Granted Patent: US 10,429,469 B2
• Time in Patent Office: Days
• US Class Current: 600/416
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: G01R 33/4818 MR characterised by data acquisition along a specific k-space trajectory or by the temporal order of k-space coverage, e.g. centric or segmented coverage of k-space
• CPC Class Codes: G01R 33/4826 in three dimensions

Abstract

A system and method for sampling k-space is provided that substantially simplifies the demands placed on the clinician to select and balance the tradeoffs of a particular selected sampling methodology. In particular, the present invention provides particularly advantageous sampling methodologies that simplify the selection of a particular k-space sampling methodology and, furthermore, the tradeoffs within a particular sampling methodology.

Claims

1. A magnetic resonance imaging (MRI) system, comprising:

a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject arranged in the MRI system;

a magnetic gradient system including a plurality of magnetic gradient coils configured to apply at least one magnetic gradient field to the polarizing magnetic field;

a radio frequency (RF) system configured to apply an RF field to the subject and to receive magnetic resonance signals therefrom;

a computer system programmed to;

control the RF system to generate a base waveform having a trajectory extending at least one of to and from an axis located at a center of k-space and a periphery of k-space;

control the RF system and the magnetic gradient system to generate a plurality of repetitions of the base waveform, each repetition of the base waveform rotationally offset by a predetermined angle about the axis with respect to adjacent repetitions of the base waveform to form a plurality of interleaved trajectories;

control the RF system and the magnetic gradient system to generate a plurality of repetitions of the plurality of interleaved trajectories initiated from initial locations aligned along the axis to sample k-space in three dimensions, wherein a cross-section of the plurality of repetitions of the plurality of interleaved trajectories extending along the axis is mirror-symmetric; and

wherein samples along the trajectory are distributed at points (kr) with radial spacing proportional to 1/√

{square root over (1−

kr²)}.

2. The system of claim 1 wherein the predetermined angle is a golden angle.

3. The system of claim 1 wherein the predetermined angle is equal to 180 degrees multiplied by a quantity of three less than the square root of 5 degrees.

4. The system of claim 1 wherein the trajectory includes a two-dimensional (2D) Archimedean spiral.

5. The system of claim 1 wherein the locations aligned along the axis are determined by kz₀(n)*√

{square root over (1−

kr²)}, where kz₀ represents an initial location along the axis.

6. The system of claim 1 wherein locations along the trajectory with respect to the axis are selected as a function of radial k-space location in a transverse plane to the axis, such that kr is equal to a square root of a sum of a first distance in the transverse plane from the axis squared and second distance in the transverse plane from the axis squared, wherein the first and second distances are determined along lines orthogonal to each other.

7. The system of claim 1 wherein the plurality of repetitions of the base waveform are played out during application of a phase encoding gradient extend the trajectory in a direction toward alignment with the axis.

8. The system of claim 7 wherein the plurality of repetitions of the plurality of interleaved trajectories is played out during application of a concurrent transverse phase encoding gradient to move the initial locations along the axis in a direction opposite the direction toward alignment with the axis and cause the periphery of k-space to follow a surface of a sphere.

9. A method comprising:

designing, with a computer system, a pulse sequence for use with a magnetic resonance imaging (MRI) system comprising;

a base waveform having a trajectory extending at least one of to and from an axis located at a center of k-space and a periphery of k-space;

a plurality of repetitions of the base waveform, each repetition of the base waveform rotationally offset by a predetermined angle about the axis with respect to adjacent repetitions of the base waveform to form a plurality of interleaved trajectories;

a plurality of repetitions of the plurality of interleaved trajectories initiated from initial locations aligned along the axis to sample k-space in three dimensions, wherein a cross-section of the plurality of repetitions of the plurality of interleaved trajectories extending along the axis is mirror-symmetric; and

wherein samples along the trajectory are distributed at points (kr) with radial spacing proportional to 1/√

{square root over (1−

kr²)}.

10. The method of claim 9 wherein the predetermined angle is a golden angle.

11. The method of claim 9 wherein the predetermined angle is equal to 180 degrees multiplied by a quantity of three less than the square root of 5 degrees.

12. The method of claim 9 wherein the trajectory includes a two-dimensional (2D) Archimedean spiral.

13. The method of claim 9 wherein the locations aligned along the axis are determined by kz₀(n)*√

{square root over (1−

kr²)}, where kz₀ represents an initial location along the axis.

14. The method of claim 9 wherein locations along the trajectory with respect to the axis are selected as a function of radial k-space location in a transverse plane to the axis, such that kr is equal to a square root of a sum of a first distance in the transverse plane from the axis squared and second distance in the transverse plane from the axis squared, wherein the first and second distances are determined along lines orthogonal to each other.

15. The method of claim 9 wherein the plurality of repetitions of the base waveform are played out during application of a phase encoding gradient extend the trajectory in a direction toward alignment with the axis.

16. The method of claim 15 wherein the plurality of repetitions of the plurality of interleaved trajectories is played out during application of a concurrent transverse phase encoding gradient to move the initial locations along the axis in a direction opposite the direction toward alignment with the axis and cause the periphery of k-space to follow a surface of a sphere.

17. A method for controlling a magnetic resonance imaging (MRI) system to acquire medical imaging data from a subject, the method comprising:

designing a pulse sequence comprising

a base waveform having a trajectory to extend at least one of to and from an axis located at a center of k-space and a periphery of k-space;

a plurality of repetitions of the base waveform, each repetition of the base waveform rotationally offset by a predetermined golden angle about the axis with respect to adjacent repetitions of the base waveform to form a plurality of interleaved trajectories;

a plurality of repetitions of the plurality of interleaved trajectories initiated from initial locations aligned along the axis to sample k-space in three dimensions, wherein a cross-section of the plurality of repetitions of the plurality of interleaved trajectories extending along the axis;

wherein samples along the trajectory are distributed at points (kr) with radial spacing;

performing the pulse sequence using the MRI system to collect medical imaging data of the subject; and

reconstructing an image of the subject from the medical imaging data.

18. The method of claim 17 wherein samples along the trajectory are distributed at points (kr) with radial spacing proportional to 1/√

{square root over (1−

kr²)}.

19. The method of claim 17 wherein the predetermined golden angle is equal to 180 degrees multiplied by a quantity of three less than the square root of 5 degrees.

20. A method for acquiring magnetic resonance imaging data comprising:

selecting a base waveform having a trajectory extending from a center of k-space toward a periphery of k-space;

performing, with a magnetic resonance imaging system, the base waveform configured to acquire medical imaging data;

repeating, with the magnetic resonance imaging system, the base waveform in a substantially consistent form, with each repetition of the base waveform, rotating the trajectory about an axis at the center of k-space by a golden angle; and

reconstructing an image from the medical imaging data.