MR IMAGING WITH MOTION DETECTION

• US 20180210058A1
• Filed: 07/13/2016
• Published: 07/26/2018
• Est. Priority Date: 07/15/2015
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: DE WEERDT, ELWIN
• Granted Patent: US 10,634,753 B2
• Time in Patent Office: Days
• CPC Class Codes: 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
• CPC Class Codes: G01R 33/4822 in three dimensions
• CPC Class Codes: G01R 33/4826 in three dimensions
• CPC Class Codes: G01R 33/5608 Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels image data processing or generation, in general G06T
• 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 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence

Abstract

The invention relates to a method of MR imaging of an object (10) placed in the examination volume of a MR device (1). It is an object of the invention to provide a method that enables efficient motion-compensation and/or motion-correction and that is compatible with Cartesian sampling of k-space. The method of the invention comprises: —generating MR signals by subjecting the object (10) to a MR imaging sequence of at least one RF pulse and switched magnetic field gradients; —acquiring the MR signals as a plurality of temporally successive subsets, each subset comprising a number of k-space profiles with sub-sampling of k-space, wherein the subsets complement each other to form a fully sampled set of k-space profiles; —reconstructing a single-subset MR image from each subset; —computing a gradient MR image from each single-subset MR image; and —detecting motion by comparing the gradient MR images with each other. Moreover, the invention relates to a MR device (1) and to a computer program for a MR device (1).

Claims

1. A method of magnetic resonance (MR) imaging of an object placed in the examination volume of a MR device, the method comprising the steps of:

generating MR signals by subjecting the object to a MR imaging sequence of at least one RF pulse and switched magnetic field gradients;

acquiring the MR signals as a plurality of temporally successive subsets, each subset comprising a number of k-space profiles with sub-sampling of k-space, wherein the subsets complement each other to form a fully sampled set of k-space profiles;

reconstructing a single-subset MR image from each subset;

computing a gradient MR image from each single-subset MR image; and

detecting motion by comparing the gradient MR images with each other.

2. The method of claim 1, further comprising:

reconstructing a motion-compensated MR image from the fully sampled set of k-space profiles, wherein the subsets are weighted according to the detected motion.

3. The method of claim 1, further comprising:

applying motion correction to at least one of the subsets according to the detected motion; and

reconstructing a motion-corrected MR image from the fully sampled set of k-space profiles formed from the motion-corrected subsets.

4. The method of claim 1, further comprising:

re-acquiring one or more motion-corrupted subsets; and

reconstructing a final MR image from the fully sampled set of k-space profiles formed from the not motion-corrupted subsets and the re-acquired subsets.

5. The method of claim 4, wherein the field-of-view of the k-space sampling is adapted in the step of re-acquiring the subsets according to the detected motion.

6. The method of claim 1, wherein the step of detecting motion includes computing the cross-correlation for each pair of gradient images.

7. The method of claim 1, wherein translation and/or rotation parameters of the detected motion are derived by comparing the gradient images with each other.

8. The method of claim 1, wherein all subsets cover the same pre-determined region of k-space.

11. The method of claim 1, wherein the imaging sequence is a multi-echo imaging sequence comprising a number of shots, wherein each subset corresponds to a train of MR echo signals generated in a single shot of the multi-echo imaging sequence.

12. The method of claim 1, wherein the subsets are acquired using non-Cartesian sampling of k-space.

13. The method of claim 1, wherein the subsets comprise three-dimensional or higher-dimensional k-space data.

14. The method of claim 1, wherein the gradient images are computed by determining spatial derivatives of the image values of the single-subset MR images along at least one spatial direction.

17. Method of claim 1, wherein in the computation of the gradient MR image involves to reduce the inner k-space'"'"'s influence, in particular in that the gradient MR image is computed as voxel-wise spatial derivative of the image values (in at least one spatial direction) of the corresponding single-subset MR image.

9. (canceled)

10. The method of claim 9, wherein the subsets are acquired using Cartesian sampling of k-space and each subset comprises a number of equidistant, parallel k-space profiles.

15. A magnetic resonance (MR) device including at least one main magnet coil for generating a uniform, steady magnetic field B0 within an examination volume, a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume, at least one RF coil for generating RF pulses within the examination volume and/or for receiving MR signals from an object positioned in the examination volume, a control unit for controlling the temporal succession of RF pulses and switched magnetic field gradients, and a reconstruction unit for reconstructing MR images from the received MR signals, wherein the MR device is configured to perform the following steps:

generating MR signals by subjecting the object to a MR imaging sequence of at least one RF pulse and switched magnetic field gradients;

acquiring the MR signals as a plurality of temporally successive subsets, each subset comprising a number of k-space profiles with sub-sampling of k-space, wherein the subsets complement each other to form a fully sampled set of k-space profiles;

reconstructing a single-subset MR image from each subset;

computing a gradient MR image from each single-subset MR image; and

detecting motion by comparing the gradient MR images with each other.

16. A computer program to be run on a MR device, which computer program comprises instructions stored on a machine readable medium for:

generating a MR imaging sequence of at least one RF pulse and switched magnetic field gradients;

acquiring MR signals as a plurality of temporally successive subsets, each subset comprising a number of k-space profiles with sub-sampling of k-space, wherein the subsets complement each other to form a fully sampled set of k-space profiles;

reconstructing a single-subset MR image from each subset;

computing a gradient MR image from each single-subset MR image; and

detecting motion by comparing the gradient MR images with each other.