Accelerated MRI with Nonlinear Spatial Encoding Gradients

• US 20120286783A1
• Filed: 12/22/2010
• Published: 11/15/2012
• Est. Priority Date: 12/22/2009
• Status: Active Grant

• Current Assignee: Yale University
• Original Assignee: Yale University
• Inventors: Tam, Lick-Kong, Constable, Robert T., Stockmann, Jason, Galiana, Gigi
• Granted Patent: US 9,229,081 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01R 33/385 using gradient magnetic field coils
• CPC Class Codes: G01R 33/5611 Parallel magnetic resonance imaging, e.g. sensitivity encoding [SENSE], simultaneous acquisition of spatial harmonics [SMASH], unaliasing by Fourier encoding of the overlaps using the temporal dimension [UNFOLD], k-t-broad-use linear acquisition speed-up technique [k-t-BLAST], k-t-SENSE structural details of arrays of sub-coils G01R33/3415

Abstract

In a method of magnetic resonance imaging, a set of nonlinear, mutually orthogonal magnetic gradient encoding fields are sequentially and separately generated in an imaging region [100]. Using multiple receiver coils having nonuniform sensitivity profiles, echo data representing signal intensities in the imaging region is sequentially acquired as the magnetic gradient encoding fields are sequentially generated [102]. A reconstructed image of the imaging region is computed from the acquired echo data [104], and the reconstructed image is then be stored and/or displayed on a display monitor [106].

Claims

1. A method of parallel magnetic resonance imaging comprising:

a) sequentially and separately generating magnetic gradient encoding fields in an imaging region;

b) sequentially acquiring echo data representing signal intensities;

c) computing a reconstructed image from the acquired echo data; and

d) displaying the computed image;

wherein the sequentially acquired echo data corresponds to the sequentially generated magnetic gradient encoding fields;

wherein multiple receiver coils are used to simultaneously acquire echo data at each instant in time;

wherein the multiple receiver coils have corresponding nonuniform receiver coil sensitivity profiles;

wherein the magnetic gradient encoding fields are nonlinear spatial gradient fields that are solutions to the Laplace equation; and

wherein the magnetic gradient encoding fields approximate ideal gradient field shapes that are optimally complementary to spatial information provided by the receiver coil sensitivity profiles.

2. The method of claim 1 wherein the magnetic gradient encoding fields approximate ideal gradient field shapes that optimally encode information residing in the null space of the coil sensitivity profiles.

3. The method of claim 1 wherein the magnetic gradient encoding fields are spherical harmonic functions or free disk harmonic functions.

4. The method of claim 1 wherein the magnetic gradient encoding fields are mutually orthogonal.

5. The method of claim 1 wherein the reconstructed image is computed using a set of linear equations relating the receiver coil sensitivity profiles, the magnetic gradient encoding fields, and acquired echo data.

6. The method of claim 1 wherein the reconstructed image is computed using an algebraic reconstruction technique.

7. The method of claim 1 wherein the magnetic gradient encoding fields are a least-squares approximation to the ideal gradient fields.