Method and system for multi-shot spiral magnetic resonance elastography pulse sequence

• US 10,261,157 B2
• Filed: 02/12/2014
• Issued: 04/16/2019
• Est. Priority Date: 02/18/2013
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois
• Original Assignee: Board of Trustees of The University of Illinois
• Inventors: Sutton, Bradley, Georgiadis, John G., Johnson, Curtis
• Primary Examiner(s): Fuller, Rodney E
• Application Number:
  US14/178,355
• Publication Number:
  US 20140232395A1
• Time in Patent Office: 1,889 Days
• Field of Search: 324309
• CPC Class Codes: G01R 33/4824 using a non-Cartesian trajectory
• CPC Class Codes: G01R 33/56358 Elastography
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence

Abstract

Aspects of the subject disclosure include a system that applies magnetic resonance elastography to a sample to obtain uncorrected k-space data where the magnetic resonance elastography utilizes a multi-shot spin-echo sequence with variable density spiral readout gradients, and adjusts the uncorrected k-space data to corrected k-space data by adjusting a k-space trajectory by shifting a center point for each shot to a new center point according to signal intensity and by adjusting a phase for each shot based on a phase offset that is determined according to the signal intensity.

Claims

1. A method comprising:

applying, by an actuator of a system including a processor, an induced vibration to a sample, wherein the induced vibration has an induced vibration period;

applying to the sample, by the system, a first motion-encoding gradient of a magnetic resonance elastography, wherein the first motion-encoding gradient has a first vibration period equal to the induced vibration period, wherein the magnetic resonance elastography utilizes a multi-shot spin-echo sequence, and wherein the magnetic resonance elastography includes a refocusing pulse;

applying to the sample, by the system, a second motion-encoding gradient of the magnetic resonance elastography, wherein the second motion-encoding gradient has a second vibration period equal to the induced vibration period, and wherein the second motion-encoding gradient is separated from the first motion-encoding gradient by one-half of the induced vibration period with the refocusing pulse between the first motion-encoding gradient and the second motion-encoding gradient;

applying to the sample, by the system, a variable density spiral readout gradient of the magnetic resonance elastography;

acquiring by the system, based upon at least a portion of the magnetic resonance elastography that is applied to the sample, a corrupted image that includes uncorrected k-space data;

adjusting, by the system, the uncorrected k-space data to corrected k-space data by;

determining a point of maximum signal intensity for each shot of the multi-shot spin-echo sequence,

adjusting a k-space trajectory by shifting a center point for each shot of the multi-shot spin-echo sequence to a corresponding point of maximum signal intensity, and

adjusting a phase for each shot of the multi-shot spin-echo sequence by applying a negative of a phase at the corresponding point of maximum signal intensity;

determining, by the system, a corrected image by applying a Fourier transform to the corrected k-space data summed over all shots of the multi-shot spin-echo sequence; and

presenting, by the system, the corrected image on a display.

2. The method of claim 1, further comprising determining a material property of the sample by applying an inversion algorithm to the corrected k-space data.

3. The method of claim 2, wherein the material property comprises a shear modulus.

4. The method of claim 1, wherein each of the first motion-encoding gradient and the second motion-encoding gradient is bipolar.

5. The method of claim 4, wherein:

the multi-shot spin-echo sequence comprises an echo time; and

the variable density spiral readout gradient has an entire readout after the echo time.

6. The method of claim 1, wherein:

the multi-shot spin-echo sequence comprises an echo time; and

the variable density spiral readout gradient has an entire readout after the echo time.

7. The method of claim 1, further comprising extracting motion at a first harmonic from the corrected k-space data using a temporal Fourier transform.

8. The method of claim 7, wherein filtering of the corrected k-space data is limited to the extracting of the motion at the first harmonic.

9. The method of claim 1, wherein the sample is an in vivo brain, wherein the multi-shot spin-echo sequence comprises at least two shots, and wherein the induced vibration is between 50 to 100 Hz applied to the in vivo brain.

10. A system comprising:

an actuator for applying an induced vibration to a sample;

a magnetic resonance system for 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, the operations comprising;

applying by the actuator the induced vibration to the sample, wherein the induced vibration has an induced vibration period;

applying by the magnetic resonance system to the sample a first motion-encoding gradient of the magnetic resonance elastography, wherein the first motion-encoding gradient has a first vibration period equal to the induced vibration period, wherein the magnetic resonance elastography utilizes a multi-shot spin-echo sequence, and wherein the magnetic resonance elastography includes a refocusing pulse;

applying by the magnetic resonance system to the sample a second motion-encoding gradient of the magnetic resonance elastography, wherein the second motion-encoding gradient has a second vibration period equal to the induced vibration period, and wherein the second motion-encoding gradient is separated from the first motion-encoding gradient by one-half of the induced vibration period with the refocusing pulse between the first motion-encoding gradient and the second motion-encoding gradient;

applying by the magnetic resonance system to the sample a variable density spiral readout gradient of the magnetic resonance elastography;

acquiring by the processor, based upon at least a portion of the magnetic resonance elastography that is applied to the sample, a corrupted image that includes uncorrected k-space data;

adjusting by the processor the uncorrected k-space data to corrected k-space data by adjusting a k-space trajectory by shifting a center point for each shot of the multi-shot spin-echo sequence to a new center point according to signal intensity and by adjusting a phase for each shot of the multi-shot spin-echo sequence based on a phase offset that is determined according to the signal intensity;

determining by the processor a corrected image by applying a Fourier transform to the corrected k-space data summed over all shots of the multi-shot spin-echo sequence; and

presenting by the processor the corrected image on a display.

11. The system of claim 10, wherein the adjusting of the k-space trajectory by shifting the center point for each shot of the multi-shot spin-echo sequence to the new center point according to the signal intensity comprises determining a point of maximum signal intensity for each shot of the multi-shot spin-echo sequence and shifting the center point for each shot of the multi-shot spin-echo sequence to a corresponding point of maximum signal intensity.

12. The system of claim 10, wherein the adjusting of the phase for each shot of the multi-shot spin-echo sequence based on the phase offset comprises determining a point of maximum signal intensity for each shot of the multi-shot spin-echo sequence and adjusting the phase for each shot of the multi-shot spin-echo sequence by applying a negative of a phase at a corresponding point of maximum signal intensity.

13. The system of claim 10, wherein the operations further comprise determining, by the processor, a material property of the sample by applying an inversion algorithm to the corrected k-space data.

14. The system of claim 13, wherein the material property comprises a shear modulus.

15. The system of claim 10, wherein:

the multi-shot spin-echo sequence comprises an echo time; and

the variable density spiral readout gradient has an entire readout after the echo time.

16. The system of claim 10, wherein the operations further comprise extracting motion, by the processor, at a first harmonic from the corrected k-space data using a temporal Fourier transform.

17. The system of claim 10, wherein the sample is an in vivo brain, wherein the multi-shot spin-echo sequence comprises at least two shots, and wherein the induced vibration is between 50 to 100 Hz applied to the in vivo brain.

18. A computer-readable storage device comprising computer instructions which, responsive to being executed by a processing system including a processor, facilitate performance of operations, the operations comprising:

applying, by an actuator coupled to the processing system, an induced vibration to a sample, wherein the induced vibration has an induced vibration period;

applying to the sample, by a magnetic resonance system coupled to the processing system, a first motion-encoding gradient of a magnetic resonance elastography, wherein the first motion-encoding gradient has a first vibration period equal to the induced vibration period, wherein the magnetic resonance elastography utilizes a multi-shot spin-echo sequence, and wherein the magnetic resonance elastography includes a refocusing pulse;

applying to the sample, by the magnetic resonance system, a second motion-encoding gradient of the magnetic resonance elastography, wherein the second motion-encoding gradient has a second vibration period equal to the induced vibration period, and wherein the second motion-encoding gradient is separated from the first motion-encoding gradient by one-half of the induced vibration period with the refocusing pulse between the first motion-encoding gradient and the second motion-encoding gradient;

applying to the sample, by the magnetic resonance system, a variable density spiral readout gradient of the magnetic resonance elastography;

acquiring by the magnetic resonance system, based upon at least a portion of the magnetic resonance elastography that is applied to the sample, a corrupted image that includes uncorrected k-space data;

adjusting by the processing system the uncorrected k-space data to corrected k-space data by adjusting a k-space trajectory by shifting a center point for each shot of the multi-shot spin-echo sequence to a new center point according to signal intensity and by adjusting a phase for each shot of the multi-shot spin-echo sequence based on a phase offset that is determined according to the signal intensity;

obtaining by the processing system a corrected image by applying a Fourier transform to the corrected k-space data summed over all shots of the multi-shot spin-echo sequence; and

presenting by the processing system the corrected image on a display.

19. The computer-readable storage device of claim 18, wherein the adjusting of the k-space trajectory by shifting the center point for each shot of the multi-shot spin-echo sequence to the new center point according to the signal intensity comprises determining a point of maximum signal intensity for each shot of the multi-shot spin-echo sequence and shifting the center point for each shot of the multi-shot spin-echo sequence to a corresponding point of maximum signal intensity, and wherein the adjusting of the phase for each shot of the multi-shot spin-echo sequence based on the phase offset comprises determining the point of maximum signal intensity for each shot of the multi-shot spin-echo sequence and adjusting the phase for each shot of the multi-shot spin-echo sequence by applying a negative of a phase at the corresponding point of maximum signal intensity.

20. The computer-readable storage device of claim 18, wherein the operations further comprise determining a material property of the sample by applying an inversion algorithm to the corrected k-space data.