THREE DIMENSIONAL MULTISLAB, MULTI-SHOT MAGNETIC RESONANCE ELASTOGRAPHY

• US 20160266225A1
• Filed: 08/07/2014
• Published: 09/15/2016
• Est. Priority Date: 10/31/2013
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois
• Original Assignee: Board of Trustees of The University of Illinois
• Inventors: JOHNSON, CURTIS L., SUTTON, BRADLEY, GEORGIADIS, JOHN G., HOLTROP, JOSEPH L.
• Granted Patent: US 10,551,464 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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
• CPC Class Codes: G01R 33/56358 Elastography
• CPC Class Codes: G01R 33/56545 caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts
• CPC Class Codes: G01R 33/5676 Gating or triggering based on an MR signal, e.g. involving one or more navigator echoes for motion monitoring and correction

Abstract

A method and system provides an acquisition scheme for generating MRE displacement data with whole-sample coverage, high spatial resolution, and adequate SNR in a short scan time. The method and system can acquire in-plane k-space shots over a volume of a sample divided into a plurality of slabs that each include a plurality of slices to obtain three dimensional multislab, multishot data, can apply refocusing pulses to the sample, can acquire navigators after the refocusing pulses, and can correct for phase errors based on an averaging of the navigators

Claims

1. A method of magnetic resonance elastography, the method comprising:

applying, by a system including a processor, a first refocusing pulse to a sample, wherein the sample is divided into a plurality of slabs that each include a plurality of slices;

applying, by the system, first and second motion encoding gradients to the sample, wherein the first motion encoding gradient is applied before the first refocusing pulse, and wherein the second motion encoding gradient is applied after the first refocusing pulse;

providing a gradient blip to define a sample plane;

acquiring, by the system, an in-plane k-space shot after the second motion encoding gradient is applied and after the gradient blip is provided; and

repeating the applying of the first refocusing pulse, the applying of the first and second motion encoding gradients and the acquiring of the in-plane k-space shot over the plurality of slabs to obtain three dimensional multislab, multishot data.

2. The method of claim 1, comprising generating a modulus map image for the sample according to the obtained three dimensional multislab, multishot data.

3. The method of claim 1, comprising:

determining a tissue relaxation time for the sample; and

calculating a repetition time according to the tissue relaxation time, wherein the obtaining of the three dimensional multislab, multishot data is according to the repetition time.

4. The method of claim 1, comprising:

applying, by the system, a second refocusing pulse to the sample after the in-plane k-space shot is acquired;

acquiring, by the system, a navigator after the second refocusing pulse is applied; and

performing, by the system, correction for phase errors, the correction being performed based on the navigator.

5. The method of claim 4, wherein the acquiring of the navigator is repeated over the plurality of slabs of the sample to acquire a plurality of navigators, wherein the correction is performed based on the plurality of navigators.

6. The method of claim 5, comprising:

averaging the plurality of navigators, wherein the correction for the phase errors is performed based on the averaging of the plurality of navigators.

7. The method of claim 1, wherein a total number of excitations is equal to a number of acquired in-plane k-space shots times a number of slices per slab, and wherein the first and second motion encoding gradients are flow-compensated.

8. The method of claim 1, wherein the obtaining of the three dimensional multislab, multishot data includes utilizing parallel imaging of the sample.

9. The method of claim 1, wherein adjacent slabs of the plurality of slabs are overlapped, and wherein data acquired for at least a portion of overlapped slices is discarded.

10. The method of claim 1, wherein the sample is an in vivo brain, wherein adjacent slabs of the plurality of slabs are overlapped by at least 25 percent, and wherein data acquired for at least a portion of overlapped slices is discarded.

11. A system comprising:

an actuator for applying a vibration to a sample;

a magnetic resonance system for facilitating applying magnetic resonance elastography to the sample;

a processor coupled with the actuator and the magnetic resonance system; and

a memory that stores executable instructions which, responsive to being executed by the processor, facilitate performance of operations, comprising;

providing a gradient blip to define a sample plane;

acquiring in-plane k-space shots over a volume of a sample divided into a plurality of slabs that each include a plurality of slices to obtain three dimensional multislab, multishot data;

applying refocusing pulses to the sample;

acquiring navigators after the refocusing pulses; and

correcting for phase errors based on an averaging of the navigators.

12. The system of claim 11, wherein the operations further comprise:

determining a tissue relaxation time for the sample; and

calculating a repetition time according to the tissue relaxation time, wherein the obtaining of the three dimensional multislab, multishot data is according to the repetition time.

13. The system of claim 11, wherein the operations further comprise:

performing parallel imaging of the sample to facilitate the obtaining of the three dimensional multislab, multishot data.

14. The system of claim 11, wherein a total number of excitations is equal to a number of acquired in-plane k-space shots times a number of slices per slab.

15. The system of claim 11, wherein the operations further comprise generating a modulus map image for the sample according to the obtained three dimensional multislab, multishot data.

16. A computer-readable storage device comprising computer instructions which, responsive to being executed by a processor, facilitate performance of operations, comprising:

applying a first refocusing pulse to a sample that is divided into a plurality of slabs that each include a plurality of slices;

applying first and second motion encoding gradients to the sample, wherein the first motion encoding gradient is applied before the first refocusing pulse, and wherein the second motion encoding gradient is applied after the first refocusing pulse;

providing a gradient blip to define a sample plane;

acquiring an in-plane k-space shot after the second motion encoding gradient is applied; and

repeating the applying of the first refocusing pulse, the applying of the first and second motion encoding gradients and the acquiring of the in-plane k-space shot over the plurality of slabs of the sample to obtain three dimensional multislab, multishot data.

17. The computer-readable storage device of claim 16, wherein the operations further comprise:

determining a tissue relaxation time for the sample; and

calculating a repetition time according to the tissue relaxation time, wherein the obtaining of the three dimensional multislab, multishot data is according to the repetition time.

18. The computer-readable storage device of claim 16, wherein the operations further comprise:

applying second refocusing pulses to the sample after each of the in-plane k-space shots are acquired;

acquiring navigators after each of the second refocusing pulses are applied;

averaging the navigators; and

correcting for phase errors based on the averaging of the navigators.

19. The computer-readable storage device of claim 16, wherein a total number of excitations is equal to a number of acquired in-plane k-space shots times a number of slices per slab.

20. The computer-readable storage device of claim 16, wherein the obtaining of the three dimensional multislab, multishot data includes utilizing parallel imaging of the sample.