BO-corrected sensitivity encoding magnetic resonance imaging

Patent metadata

Field	Value
Publication number	US-10955508-B2
Application number	US-201716326398-A
Country	US
Kind code	B2
Filing date	Aug 22, 2017
Priority date	Aug 25, 2016
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

A magnetic resonance imaging system (200, 300, 400) includes a radio-frequency system (216, 214) with multiple coil elements (214) for acquiring magnetic resonance data (264) and a memory (250) for storing machine executable instructions (260) and pulse sequence commands (262). The pulse sequence commands are configured for controlling the magnetic resonance imaging system to acquire the magnetic resonance data according to a SENSE imaging protocol. Execution of the machine executable instructions causes a processor (244) to: control (500) the magnetic resonance imaging system to acquire the magnetic resonance data using the pulse sequence commands; reconstruct (502) a set of folded magnetic resonance images (266) from the magnetic resonance data; calculate (504) a voxel deformation map (270) from a magnetic field inhomogeneity map; and calculate (506) a set of unfolding matrices (274) using a least partially a coil sensitivity matrix (272) for the multiple coil elements, wherein the set of unfolding matrices includes at least one modified unfolding matrix which is calculated at least partially using the a coil sensitivity matrix and the voxel deformation map. Undistorted magnetic resonance image data (276) is calculated (508) using the set of folded magnetic resonance images and the set of unfolding matrices.

First claim

The invention claimed is:

1. A magnetic resonance imaging system comprising:
a radio-frequency system comprising multiple coil elements for acquiring magnetic resonance data;
a non-transitory computer readable memory configured to store machine executable instructions and pulse sequence commands, wherein the pulse sequence commands are configured for controlling the magnetic resonance imaging system to acquire the magnetic resonance data according to a SENSE imaging protocol that is associated with folding effects due to under sampling in k-space of the magnetic resonance data,
a processor for controlling the magnetic resonance imaging system, wherein execution of the machine executable instructions causes the processor to:
control the magnetic resonance imaging system to acquire the magnetic resonance data using the pulse sequence commands;
reconstruct a set of folded magnetic resonance images from the magnetic resonance data;
calculate a voxel deformation map from a magnetic field inhomogeneity map;
calculate a set of unfolding matrices using at least partially a coil sensitivity matrix for the multiple coil elements, wherein the set of unfolding matrices comprises at least one modified unfolding matrix, wherein the at least one modified unfolding matrix is calculated using the coil sensitivity matrix and the voxel deformation map;
wherein the at least one modified unfolding matrix corrects folding-like artifacts due to inhomogeneities in the magnetic field;
calculate undistorted magnetic resonance image data using the set of folded magnetic resonance images and the set of unfolding matrices including the at least one modified unfolding matrix; and
calculate modified magnetic resonance image data by transforming the undistorted magnetic resonance image data with the voxel deformation map to incorporate the magnetic field inhomogeneity back into the undistorted magnetic resonance image data.

2. The magnetic resonance imaging system of claim 1 , further including a display device configured to selectively display an undistorted image and an image with the magnetic field homogeneity incorporated back in.

3. The magnetic resonance imaging system of claim 1 , wherein calculating the modified unfolding matrix includes transforming the coil sensitivity matrix with the voxel deformation map.

4. The magnetic resonance imaging system of claim 1 , wherein the SENSE imaging protocol is an echo planar imaging protocol, wherein the echo planar imaging protocol is configured for acquiring magnetic resonance data with phase encoding in at least one phase encoding direction, wherein the voxel deformation map is descriptive of a local magnetic field distortion in the at least one phase encoding direction.

5. The magnetic resonance imaging system of claim 1 , wherein the at least one phase encoding direction is two phase encoding directions, wherein the SENSE imaging protocol is a three-dimensional SENSE imaging protocol, wherein one of the two orthogonal phase encoding directions is configured for slice selection.

6. The magnetic resonance imaging system of claim 1 , wherein the SENSE imaging protocol is a simultaneous multiple slice acquisition imaging protocol.

7. The magnetic resonance imaging system of claim 1 , wherein the modified unfolding matrix is formulated in a feed forward format.

8. The magnetic resonance imaging system of claim 7 , wherein the modified unfolding matrix is at least partially calculated using a regularization term.

9. The magnetic resonance imaging system of claim 1 , wherein the SENSE imaging protocol is a multi-shot SENSE imaging protocol.

10. The magnetic resonance imaging system of claim 1 , wherein the voxel deformation map is calculated using the pulse sequence commands and the magnetic field inhomogeneity map.

11. The magnetic resonance imaging system of claim 1 , wherein execution of the machine executable instructions further causes the processor to:
acquiring preliminary magnetic resonance data using a coil sensitivity measuring magnetic resonance imaging protocol; and
calculate the coil sensitivity matrix using the preliminary magnetic resonance data.

12. The magnetic resonance imaging system of claim 1 , wherein execution of the machine executable instructions further cause the processor to:
acquiring magnetic field magnetic resonance data using a magnetic field measuring magnetic resonance imaging protocol; and
calculate the magnetic field inhomogeneity map using the magnetic field magnetic resonance data.

13. A computer program product comprising:
machine executable instructions stored on a non-transitory computer readable medium for execution by a processor for controlling a magnetic resonance imaging system, wherein the magnetic resonance imaging system comprises a radio-frequency system comprising multiple coil elements acquiring magnetic resonance data, to control the magnetic resonance imaging system to perform the method comprising:
controlling the magnetic resonance imaging system to acquire the magnetic resonance data using pulse sequence commands, wherein the pulse sequence commands are configured for controlling the magnetic resonance imaging system to acquire the magnetic resonance data according to a SENSE imaging protocol that is associated with folding artifacts due to under sampling in k-space of the magnetic resonance data due to magnetic field inhomogeneities;
reconstructing a set of folded magnetic resonance images from the magnetic resonance data;
calculating a voxel deformation map from a magnetic field inhomogeneity map;
calculating at least one unfolding matrix using a coil sensitivity matrix for the multiple coil elements;
calculating at least one modified unfolding matrix using the coil sensitivity matrix and the voxel deformation map to correct for the folding artifacts due to inhomogeneities in the magnetic field;
calculating undistorted magnetic resonance image data using the folded magnetic resonance images, the at least one unfolding matrix, and the at least one modified unfolding matrix;
controlling a display to selectively display an image corrected for folding artifacts attributable to the magnetic field inhomogeneities as well as the under sampling in k-space and an image incorporating the magnetic field inhomogeneity; and
calculating modified magnetic resonance image data by transforming the undistorted magnetic resonance image data with the voxel deformation map to incorporate the magnetic field inhomogeneity back into the undistorted magnetic resonance image data.

14. A method of magnetic resonance imaging using a magnetic resonance imaging system including a radio-frequency system with multiple coil elements for acquiring magnetic resonance data, the method comprising:
controlling the magnetic resonance imaging system to acquire the magnetic resonance data using pulse sequence commands, wherein the pulse sequence commands are configured for controlling the magnetic resonance imaging system to acquire the magnetic resonance data according to a SENSE imaging protocol that is associated with folding artifacts due to under sampling in k-space of the magnetic resonance data due to magnetic field inhomogeneities;
reconstructing a set of folded magnetic resonance images from the magnetic resonance data;
calculating a voxel deformation map from a magnetic field inhomogeneity map;
calculating at least one unfolding matrix using a coil sensitivity matrix for the multiple coil elements;
calculating at least one modified unfolding matrix using the coil sensitivity matrix and the voxel deformation map to correct for the folding artifacts due to inhomogeneities

Assignees

• Koninklijke Philips Nv

Inventors

• Fuderer Miha
• De Weerdt Elwin
• Ermes Jean-Pierre Franciscus Alexander Maria

Classifications

• G01R33/5611 Primary

  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) · CPC title

• G01R33/56554

  caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI · CPC title

• G01R33/56536

  due to magnetic susceptibility variations · CPC title

• G01R33/56563

  caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title

• G01R33/5612 Primary

  Parallel RF transmission, i.e. RF pulse transmission using a plurality of independent transmission channels · CPC title