# US 10,871,534 B2 · Accelerated magnetic resonance imaging using a tilted reconstruction kernel in phase encoded and point spread function encoded K-space

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- Number: US 10,871,534 B2
- Document ID: US10871534B2
- Status: Granted
- Kind: B2
- Application number: 16/429,467
- Filed: 2019-06-03
- Published: 2019-12-05
- Granted: 2020-12-22
- Earliest claimed: 2018-06-01
- Assignees: The General Hospital Corporation
- Applicants: The General Hospital Corporation
- Inventors: Kawin Setsompop; Lawrence L. Wald; Zijing Dong; Hua Guo; Fuyixue Wang; Timothy G. Reese
- Web page: https://patentgrep.com/patent/US10871534B2

## CPC

- 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}
- 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)}
- G01R 33/50: based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences}
- G01R 33/5619: {by temporal sharing of data, e.g. keyhole, block regional interpolation scheme for k-Space [BRISK]}
- G01R 33/565: Correction of image distortions, e.g. due to magnetic field inhomogeneities
- G01R 33/5616: {using gradient refocusing, e.g. EPI}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

Systems and methods for accelerated magnetic resonance imaging using a tilted reconstruction kernel to synthesize unsampled k-space data in phase encoded and point spread function (“PSF”) encoded k-space data are provided. Images reconstructed from the data have reduced B0-related distortions and reduced T2* blurring. In general, data are acquired with systematically optimized undersampling of the PSF and phase encoding subspace. Parallel imaging reconstruction is implemented with a B0 inhomogeneity informed approach to achieve greater than twenty-fold acceleration of the PSF encoding dimension. A tilted reconstruction kernel is used to exploit the correlations in the phase encoding-PSF encoding subspace.

## Claims

### Claim 1

A method for reconstructing an image of a subject from data acquired with a magnetic resonance imaging (MRI) system, the steps of the method comprising:
(a) acquiring first data with a magnetic resonance imaging (MRI) system, wherein the first data comprise k-space data encoded along at least a phase encoding dimension and a point spread function (PSF) encoding dimension and wherein the first data are undersampled along at least one of the phase encoding dimension or the PSF encoding dimension;
(b) generating second data with a computer system by synthesizing unsampled k-space points in at least one of the phase encoding dimension or the PSF encoding dimension by applying a tilted reconstruction kernel to the first data, wherein the tilted reconstruction kernel spans the phase encoding dimension and the PSF encoding dimension;
(c) reconstructing an image from the second data.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein the tilted reconstruction kernel is tilted at an angle relative to at least one of the phase encoding dimension and the PSF encoding dimension.

### Claim 3 (depends on 2)

The method as recited in claim 2, wherein the tilted reconstruction kernel is tilted at a 45 degree angle relative to the PSF encoding dimension.

### Claim 4 (depends on 1)

The method as recited in claim 1, wherein step (b) jointly synthesizes unsampled k-space points in both the phase encoding dimension and the PSF encoding dimension.

### Claim 5 (depends on 1)

The method as recited in claim 1, wherein the tilted reconstruction kernel is structured to exploit correlations between the phase encoding dimension and the PSF encoding dimension.

### Claim 6 (depends on 1)

The method as recited in claim 1, wherein the first data are acquired using a PSF echo planar imaging (EPI) pulse sequence that acquires multiple phase encodings for each of a plurality of different PSF encodings.

### Claim 7 (depends on 6)

The method as recited in claim 6, wherein the PSF EPI pulse sequence includes a PSF-encoding loop that samples a point on the PSF encoding dimension at a plurality of different points on the phase encoding dimension.

### Claim 8 (depends on 1)

The method as recited in claim 1, further comprising providing calibration data to the computer system and using the calibration data when synthesizing the unsampled k-space points.

### Claim 9 (depends on 8)

The method as recited in claim 8, wherein the first data are acquired using a first pulse sequence having a first echo spacing, and the calibration data are acquired using a second pulse sequence having a second echo spacing that is the same as the first echo spacing.

### Claim 10 (depends on 9)

The method as recited in claim 9, wherein the first pulse sequence and the second pulse sequence are both a PSF echo planar imaging (EPI) pulse sequence, and wherein the calibration data are acquired with a lower resolution than the first data.

### Claim 11 (depends on 1)

The method as recited in claim 1, wherein the first data comprise k-space data in which alternating phase encoding lines are shifted relative to each other.

### Claim 12 (depends on 11)

The method as recited in claim 11, wherein alternating phase encoding lines are shifted along the phase encoding dimension relative to each other.

### Claim 13 (depends on 1)

The method as recited in claim 1, wherein synthesizing the unsampled k-space points includes using a GRAPPA algorithm that implements the tilted reconstruction kernel.

### Claim 14 (depends on 1)

The method as recited in claim 1, wherein encoding the k-space data along the phase encoding dimension and the PSF encoding dimension both implement magnetic field gradients applied along a same spatial direction.

### Claim 15 (depends on 1)

The method as recited in claim 1, wherein the image reconstructed in step (c) has reduced distortions and T2* blurring relative to images reconstructed from the first data.