Parallel mri with bo distortion correction and multi-echo dixon water-fat separation using regularised sense reconstruction

Patent metadata

Field	Value
Publication number	US-2016124064-A1
Application number	US-201414895006-A
Country	US
Kind code	A1
Filing date	Jun 5, 2014
Priority date	Jun 6, 2013
Publication date	May 5, 2016
Grant date	—

Abstract

The invention relates to a method of MR imaging of an object positioned in an examination volume of a MR device ( 1 ). The method comprises the steps of: acquiring reference MR signal data from the object ( 10 ); deriving a Bo map from the reference MR signal data; adapting sensitivity maps according to the B0 map, which sensitivity maps indicate spatial sensitivity profiles of one or more RF receiving coils ( 11, 12, 13 ), to correct for geometric distortions of the sensitivity maps; acquiring imaging MR signal data from the object ( 10 ) via the one or more receiving coils ( 11, 12, 13 ) with sub-sampling of k-space; and reconstructing a MR image from the imaging MR signal data, wherein sub-sampling artefacts are eliminated using the adapted sensitivity maps. In a preferred embodiment, the reference MR signal data are acquired using a multi-point Dixon technique, wherein a water map and a fat map are derived from the reference MR signal data. A water image and a fat image are reconstructed from the imaging MR signal data using separate water and fat sensitivity maps. The water and fat images are preferably reconstructed using regularised SENSE, wherein a water regularisation map and a fat regularisation map are derived from the multi-point Dixon reference MR signal data. Moreover, the invention relates to a MR device ( 1 ) for carrying out the method, and to a computer program to be run on a MR device ( 1 ).

First claim

1 . A method of magnet resonance (MR) imaging of an object positioned in an examination volume of a MR device, the method comprising the steps of:
acquiring reference MR signal data from the object using a multi-point Dixon technique and by way of two or more RF receiving coils having sensitivity maps that indicate their spatial sensitivity profiles; deriving a B 0 map from the reference MR signal data; deriving a multi-point Dixon water map and a multi-point Dixon fat map from the reference MR signal data; correcting the sensitivity maps according to the B 0 map, which for geometric distortions of the sensitivity maps; acquiring imaging MR signal data from the object via the one or more receiving coils with sub-sampling of k-space; reconstructing a MR image from the imaging MR signal data, wherein sub-sampling artefacts are eliminated using the corrected sensitivity maps, wherein the correction of the sensitivity maps includes computation of separate corrected sensitivity maps associated with signals from water and from fat, respectively and the reconstruction of the MR image is performed by way of a regularised SENSE reconstruction scheme which employs the corrected sensitivity maps to simultaneously unfold a separate water image and a fat image and the regularisation employs as a regularisation map the multi-point Dixon water map and the multi-point Dixon fat map derived form the reference MR signal data.

2 . The method of claim 1 , wherein the reference MR signal data are acquired at an image resolution that is lower than the image resolution of the imaging MR signal data.

3 . The method of claim 1 , wherein the reference MR signal data and/or the imaging MR signal data are acquired by using echo planar imaging.

4 . (canceled)

5 . The method of claim 1 , wherein a fat fraction is computed from the water map and the fat map, which fat fraction indicates the relation of the signal contributions of water and fat protons at each image position, wherein the fat fraction is used in the step of reconstructing the MR image.

6 . The method of claim 5 , wherein the water image is reconstructed using a water sensitivity map, and the fat image is reconstructed using a fat sensitivity map that is different from the water sensitivity map.

7 . The method of claim 6 , wherein the fat sensitivity map is computed from the water sensitivity map by a translation in the direction of a fat shift.

8 . (canceled)

9 . (canceled)

10 . The method of claim 1 , wherein the water image is reconstructed using a water regularisation map, and the fat image is reconstructed by using a fat regularisation map.

11 . The method of claim 1 , wherein the water regularisation map is derived from the water map, and fat regularisation map is derived from the fat map.

12 . (canceled)

13 . A MR device for carrying out the method claimed in claim 1 , wherein the MR device includes at least one main magnet coil for generating a uniform, steady magnetic field B 0 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, one or more receiving coils 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, wherein the MR device is arranged to perform the following steps:
acquiring reference MR signal data from the object using a multi-point Dixon technique by way of two or more RF receiving coils having sensitivity maps that indicate their spatial sensitivity profiles; deriving a B 0 map from the reference MR signal data; deriving a multi-point Dixon water map and a multi-point Dixon fat map from the reference MR signal data; correcting sensitivity maps according to the B 0 map, for geometric distortions of the sensitivity maps; acquiring imaging MR signal data from the object via the one or more receiving coils with sub-sampling of k-space; reconstructing a MR image from the imaging MR signal data, wherein sub-sampling artefacts are eliminated using the adapted sensitivity maps, characterised in that the correction of the sensitivity maps includes computation of separate corrected sensitivity maps associated with signals from water and from fat, respectively and the reconstruction of the MR image is performed by way of a regularised SENSE reconstruction scheme which employs the corrected sensitivity maps to simultaneously unfold a separate water image and a fat image and the regularisation employs as a regularisation map the multi-point Dixon water map and the multi-point Dixon fat map derived form the reference MR signal data.

14 . A non-transitory computer-readable medium embodying a computer program computer program to be run on a MR device, which computer program comprises instructions for:
acquiring reference MR signal data from an object using a multi-point Dixon technique and by way of two or more RF receiving coils having sensitivity maps that indicate their spatial sensitivity profiles; deriving a B 0 map from the reference MR signal data; Deriving a multi-point Dixon water map and a multi-point Dixon fat map from the reference MR signal data; correcting the sensitivity maps according to the B 0 map, for geometric distortions of the sensitivity maps; acquiring imaging MR signal data from the object via the one or more receiving coils with sub-sampling of k-space; reconstructing a MR image from the imaging MR signal data, wherein sub-sampling artefacts are eliminated using the corrected sensitivity maps characterised in that the correction of the sensitivity maps includes computation of separate corrected sensitivity maps associated with signals from water and from fat, respectively and the reconstruction of the MR image is performed by way of a regularised SENSE reconstruction scheme which employs the corrected sensitivity maps to simultaneously unfold a separate water image and a fat image and the regularisation employs as a regularisation map a multi-point Dixon water map and/or a multi-point Dixon fat map derived from the reference MR signal data.

Assignees

• Koninkl Philips Nv

Inventors

• De Weerdt Elwin
• Koppelman Steven
• Peeters Johannes Martinus

Classifications

• G01R33/5608 Primary

  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

• G01R33/5607

  by reducing the NMR signal of a particular spin species, e.g. of a chemical species for fat suppression, or of a moving spin species for black-blood imaging · CPC title

• G01R33/5611

  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 title

• G01R33/4828

  Resolving the MR signals of different chemical species, e.g. water-fat imaging · CPC title

• G01R33/243

  Spatial mapping of the polarizing magnetic field · CPC title