Optimised generation of MRI images by a multi-antenna MRI system

Patent metadata

Field	Value
Publication number	US-11143729-B2
Application number	US-201816757035-A
Country	US
Kind code	B2
Filing date	Oct 15, 2018
Priority date	Oct 18, 2017
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

The present invention improves the quality of the magnitude and phase images produced in medical imaging, in particular in the case of multi-antenna MRI. The invention proposes to generate (28) such an image (I) by summing the complex image data (pj,{tilde over (p)}j) obtained from different antennas by weighting these data using only the diagonal elements (Rj,j) of an antenna noise covariance matrix or its inverse or pseudo-inverse matrix (Rj,j−1). A reference antenna (Ref) may be determined (24), so as to be able to replace (26), in each of these datum, a phase component specific to the acquisition antenna by a reference phase component. The reference antenna is preferably a virtual antenna formed by linear combination of the antennas of the MRI system. If significant improvements are obtained in the phase image resulting from the summation, a very clear gain is also surprisingly obtained in the magnitude image.

First claim

The invention claimed is:

1. Method for generating an image of a subject using a system of nuclear magnetic resonance imaging (MRI) comprising a plurality of radio frequency receiving antennas, wherein the method comprises the following steps:
obtaining complex image data of the subject using each antenna,
obtaining a noise covariance matrix comprising one or more non-zero non-diagonal coefficients from said plurality of radio frequency receiving antennas, and
generating an image of the subject by summing the complex image data obtained using different antennas by weighting the complex image data using only diagonal elements of the noise covariance matrix or its inverse or pseudo-inverse matrix, wherein each complex datum image obtained using an antenna is weighted by a diagonal element of the noise covariance matrix or its inverse or pseudo-inverse matrix corresponding to the antenna.

2. Method according to claim 1 , wherein the step of obtaining complex image data comprises the steps of:
determining a reference antenna, and
replacing, in each complex image datum obtained using an antenna, a phase component specific to the antenna by a phase component of the reference antenna at the same spatial position as the complex image data.

3. Method according to claim 2 , wherein the reference antenna is a virtual antenna formed by linear combination of said plurality of radio frequency receiving antennas of the MRI system.

4. Method according to claim 3 , wherein the determination by linear combination comprises a correction of phases of the complex image data.

5. Method according to claim 4 , wherein the correction of complex image data obtained using an antenna is carried out independently of the other antennas, using antenna weighting coefficients chosen from the complex image data obtained using only said antenna.

6. Method according to claim 4 , wherein the correction comprises subtracting, from the complex image data obtained using said antenna, the phase of the sum of the complex image data obtained using said antenna.

7. Method according to claim 4 , wherein the linear combination is obtained by weighting the complex corrected image data as a function of the magnitude of the complex image data.

8. Method according to claim 2 , wherein the replacing step comprises applying a low-pass filter to a phase difference between a complex image datum obtained using an antenna and corresponding complex data obtained for the reference antenna, and subtracting a filtered phase difference from the phase component specific to the antenna.

9. Method according to claim 1 , wherein the image of the subject is a magnitude image or a phase image or an image with complex values.

10. Nuclear magnetic resonance imaging (MRI) system comprising a plurality of radio frequency receiving antennas and at least one processor configured to:
obtain a complex data image of a subject using each antenna,
obtain a noise covariance matrix of each antenna, wherein the noise covariance matrix comprises one or more non-zero non-diagonal coefficients,
and
generate an image of the subject by summing the complex image data obtained using different antennas by weighting the complex image data using only diagonal elements of the noise covariance matrix or its inverse or pseudo-inverse matrix, wherein each complex image datum obtained using an antenna is weighted by a diagonal element of the noise covariance matrix or its inverse or pseudo-inverse matrix corresponding to the antenna.

Assignees

• Inst Du Cerveau Et De La Moelle Epiniere Icm
• Centre Nat Rech Scient
• Inst Nat Sante Rech Med
• Assist Publique Hopitaux De Paris Ap Hp
• Univ Sorbonne
• Assist Publique—Hopitaux De Paris Ap Hp

Inventors

• Santin Mathieu

Classifications

• G01R33/5659

  caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title

• G01R33/5611 Primary

  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 title

• G01R33/5608

  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 title