Reduction of motion artifact in nmr images using spherical navigator signals

• US 20030153826A1
• Filed: 02/04/2003
• Published: 08/14/2003
• Est. Priority Date: 04/26/2000
• Status: Active Grant

• Current Assignee: Mayo Foundation For Medical Education And Research (Mayo Clinic)
• Original Assignee: Mayo Foundation For Medical Education And Research (Mayo Clinic)
• Inventors: Jack, Clifford r, Welch, Edward B, Manduca, Armando, Grimm, Roger
• Granted Patent: US 7,127,092 B2
• Time in Patent Office: Days
• US Class Current: 600/410
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• 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
• CPC Class Codes: Y10T 436/24 Nuclear magnetic resonance, electron spin resonance or other spin effects or mass spectrometry

Abstract

A series of fMRI image frames are acquired along with interleaved navigator signals. The navigator signals are acquired while three orthogonal readout gradients are applied such that a spherical surface is sampled in k-space. The navigator signals are analyzed to measure subject rotational and translational motion during the scan.

Claims

1. A method for detecting movement of a subject during a scan in which NMR image data is acquired with a magnetic resonance imaging system, the steps comprising:

a) acquiring the NMR image data using a series of NMR imaging pulse sequences;

b) interleaving with the series of NMR imaging pulse sequences a series of NMR navigator signal pulse sequences, each navigator signal pulse sequence including the application of three orthogonal magnetic field gradients during the readout of its NMR navigator signal such that a resulting NMR navigator signal samples a three-dimensional surface in k-space;

c) acquiring the NMR navigator signals during the scan; and

d) analyzing the acquired NMR navigator signals to measure motion of the subject during the scan.

2. The method as recited in claim 1 in which the three-dimensional surface is substantially spherical in shape.

3. The method as recited in claim 1 in which the three-dimensional surface is substantially hemispherical in shape.

4. The method as recited in claim 2 in which the spherical surface is centered around the origin of k-space.

5. The method as recited in claim 1 in which step d) includes:

i) registering an acquired NMR navigator signal with a reference NMR navigator signal to determine rotation of the subject; and

ii) determining the phase difference between the registered acquired NMR navigator signal and the reference NMR navigator signal to determine translation of the subject.

6. The method as recited in claim 1 in which the measured motion includes both rotation of the subject and translation of the subject.

7. The method as recited in claim 6 which includes:

calculating corrective values from the measured subject rotation and subject translation; and

correcting NMR image data using the corrective values.

8. The method as recited in claim 7 in which the NMR image data is corrected after its acquisition.

9. The method as recited in claim 1 in which two of the magnetic field gradients applied during the navigator signal pulse sequence vary sinusoidally during the readout of its navigator signal to produce a spiral sampling trajectory.

10. The method as recited in claim 9 in which the third magnetic field gradient applied during the navigator signal pulse sequence varies such that the spiral sampling trajectory defines at least a portion of a substantially spherical three-dimensional surface.

11. The method as recited in claim 1 in which 1000 to 2000 samples of said three-dimensional surface in k-space are acquired by the navigator signal.

12. The method as recited in claim 7 in which the NMR image data is corrected prior to its acquisition.

13. The method as recited in claim 10 in which the portion is at least 85% of a spherical surface.

14. The method as recited in claim 7 in which the NMR image data acquired in step a) is processed by reconstructing a time series of images;

and in which the NMR navigator signal pulse sequence is performed prior to the acquisition of NMR image data for each of the reconstructed images.

15. A method for acquiring fMRI data from a subject with a magnetic resonance imaging (MRI) system, the steps comprising:

a) acquiring NMR image data by performing a series of NMR imaging pulse sequences with the MRI system;

b) forming the acquired NMR image data into a series of data sets from which a corresponding series of images may be reconstructed;

c) interleaving with the series of NMR imaging pulse sequences a series NMR navigator signal pulse sequences, each navigator signal pulse sequence being associated with a data set and including the application of three orthogonal magnetic field gradients during the readout of its NMR navigator signal such that a resulting NMR navigator signal samples a portion of a substantially three-dimensional spherical surface in k-space;

d) acquiring each NMR navigator signal and with respect to each;

i) analyzing the NMR navigator signal to measure motion of the subject;

ii) calculating corrective values from the measured subject motion; and

iii) correcting the NMR image data in its associated data set using the corrective values.

16. The method as recited in claim 15 in which step d)i) includes:

registering the NMR navigator signal with a reference NMR navigator signal to determine rotation of the subject; and

determining the phase difference between the registered NMR navigator signal and the reference NMR navigator signal to determine translation of the subject.