Parallel MRI with spatially misregistered signal

Patent metadata

Field	Value
Publication number	US-10534060-B2
Application number	US-201313914160-A
Country	US
Kind code	B2
Filing date	Jun 10, 2013
Priority date	Jun 10, 2013
Publication date	Jan 14, 2020
Grant date	Jan 14, 2020

Abstract

A magnetic resonance imaging (MRI) system, method and/or computer readable medium is configured to effect improved parallel MR imaging with reduced unfolding artifacts by using either or both of:
(a) an unfolded “intermediate” diagnostic image to create a more accurate mask for use in further processing raw image data for final unfolded diagnostic images; and/or (b) an extension of coil sensitivity maps by replication (rather than curve-fitted extrapolation) for use in final unfolding of diagnostic images.

First claim

What is claimed is:

1. A magnetic resonance imaging (MRI) system configured for effecting parallel MR imaging with reduced unfolding artifacts of spatially misregistered signals, said MRI system comprising:
an MRI gantry including a static magnetic field coil, gradient magnetic field coils, at least one radio frequency (RF) coil configured to transmit RF signals into an imaging volume, and a plurality of RF receiver coils configured to receive nuclear magnetic resonance (NMR) RF signals from an object located in the imaging volume;
at least one digital data processing unit coupled to receive digital data from said plurality of RF receiver coils, said at least one digital data processing unit also being configured to:
generate a coil sensitivity map corresponding to each of the plurality of receiving RF coils based upon a prescan of local sensitivity data provided from a preparation MRI scan (prescan) of the object;
unfold diagnostic MRI scan data provided from a diagnostic MRI scan of the object in order to generate a diagnostic MRI image, the unfolding using a parallel imaging matrix inversion of a sensitivity matrix based on said generated coil sensitivity maps; and
output the diagnostic MRI image onto a display or into storage within a nontransient digital data storage medium or onto an outbound data transmission,
wherein, said at least one digital data processing unit has been further configured to effect either or both of:
(a) extending said coil sensitivity maps by identifying a boundary of the object in the generated coil sensitivity maps or the preparation MRI prescan of local sensitivity data, and replicating the preparation MRI prescan of local sensitivity map data beyond said identified boundary; and/or
(b) unfolding the diagnostic MRI scan data in order to generate the diagnostic MRI image by preliminarily unfolding the diagnostic MRI scan data in order to define a boundary of a mask image based on measured MRI signal intensities, and using the defined boundary of the mask image in order to mask the diagnostic MRI scan data prior to unfolding the masked diagnostic MRI scan data into the diagnostic MRI image by using said parallel imaging matrix inversion.

2. The MRI system as in claim 1 , wherein said at least one digital data processing unit is configured to effect at least said extending of the coil sensitivity maps by (a) replication, and wherein a direction of the coil sensitivity map extension by replication is in a direction of MRI phase encoding of said diagnostic MRI scan.

3. The MRI system as in claim 1 , wherein said at least one digital data processing unit is configured to effect both limitation (a) extending of the generated coil sensitivity maps and limitation (b) unfolding, by said preliminarily unfolding, of the diagnostic MRI scan data, and to:
(c) extend the generated coil sensitivity maps by replication in at least one direction;
(d) generate the mask image for the object based upon an unfolded intermediate copy of the diagnostic MRI scan data; and
(e) thereafter unfold said diagnostic MRI scan data into the diagnostic MRI image based upon both the generated extended coil sensitivity maps of (c), and the generated mask image of (d).

4. The MRI system as in claim 1 , wherein said at least one digital data processing unit is configured to effect at least said extending of the generated coil sensitivity maps, and to extend the generated coil sensitivity maps by replicating points selected from within an area defined by a detected edge corresponding to the object.

5. The MRI system as in claim 4 , wherein the at least one digital data processing unit is further configured to extend the generated coil sensitivity maps into a desired field of view (FOV).

6. The MRI system as in claim 1 , wherein the at least one digital data processing unit is configured to effect at least said unfolding of the diagnostic MRI scan data by said preliminarily unfolding, and configured to unfold at least one unmasked intermediate diagnostic data image from said diagnostic MRI scan in order to generate the mask image which is thereafter used in order to unfold a masked copy of diagnostic image data from said diagnostic MRI scan.

7. The MRI system as in claim 1 , wherein the diagnostic MRI scan is an echo planar imaging (EPI) scan.

8. The MRI system as in claim 1 , wherein the at least one digital data processing unit is configured to effect at least said extending of the generated coil sensitivity maps, and configured to use the generated coil sensitivity maps based upon the preparation MRI prescan data provided from one prescan of the object in order to unfold diagnostic magnetic resonance image scan data generated based upon further MRI scan data obtained from a plurality of further MRI scans.

9. The MRI system as in claim 1 , wherein the at least one digital data processing unit is configured to effect at least said unfolding of the diagnostic MRI scan data by said preliminarily unfolding, and configured to, when a plurality of further diagnostic MRI scans of the object are performed, use the mask image generated in a selected one of the further diagnostic MRI scans in unfolding the respective diagnostic MRI scan data of the non-selected others of the further diagnostic MRI scans.

10. The MRI system as in claim 1 , wherein the at least one digital data processing unit is configured to effect at least said unfolding of the diagnostic MRI scan data by said preliminarily unfolding, and configured to unfold the diagnostic MRI scan data based upon a Nyquist map generated from EPI Nyquist prescan images that have been obtained from a second MRI prescan of the object.

11. A magnetic resonance imaging (MRI) method configured for effecting parallel MR imaging with reduced unfolding artifacts of spatially misregistered signals, said MRI method comprising:
placing an object into an MRI gantry including a static magnetic field coil, gradient magnetic field coils, at least one radio frequency (RF) coil configured to transmit RF signals into an imaging volume, and a plurality of RF receiver coils configured to receive nuclear magnetic resonance (NMR) RF signals from said object when located in the imaging volume;
generating with at least one digital data processing unit, a coil sensitivity map corresponding to each of the plurality of receiving RF coils based upon a prescan of local sensitivity data provided from a preparation MRI scan (prescan) of the object;
unfolding diagnostic MRI scan data provided from a diagnostic MRI scan of the object in the at least one digital data processing unit order to generate a diagnostic MRI image, the unfolding using a parallel imaging matrix inversion of a sensitivity matrix based on said generated coil sensitivity maps; and
outputting the diagnostic MRI image onto a display or into storage within a non-transient digital data storage medium or onto an outbound data transmission,
wherein, said method effects either or both of:
(a) extending said generated coil sensitivity maps by identifying a boundary of the object in the generated coil sensitivity maps or the preparation MRI prescan of local sensitivity data, and replicating the preparation MRI prescan of local sensitivity map data beyond said identified boundary; and/or
(b) unfolding of the diagnostic MRI scan data in order to generate the diagnostic MRI image by a preliminarily unfolding of the diagnostic MRI scan data along with defining a boundary of a mask image based on measured MRI signal intensities, and using the defined boundary of the mask image in order to mask the diagnostic MRI scan data prior to unfolding the masked diagnostic MRI scan data into the diagnostic MRI image Fusing said parallel imagin

Assignees

• Toshiba Medical Sys Corp

Inventors

• Dannels Wayne R

Classifications

• 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

• G01R33/56554 Primary

  caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI · CPC title

• G01R33/34

  Constructional details, e.g. resonators {, specially adapted to MR} · CPC title

• A61B5/055 Primary

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G01R33/385

  using gradient magnetic field coils · CPC title