Method and apparatus for recording a magnetic resonance data set

Patent metadata

Field	Value
Publication number	US-10012715-B2
Application number	US-201514683561-A
Country	US
Kind code	B2
Filing date	Apr 10, 2015
Priority date	Apr 10, 2014
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

In a method and apparatus for recording a magnetic resonance data set of a target region of an object, wherein the target region contains at least one interfering object with a susceptibility difference from the rest of the target region that influences the homogeneity of the basic magnetic field, in particular a metal object and/or an air inclusion, in addition to a first raw data set of the target region recorded without additional dephasing, at least one further raw data set of the target region is recorded that corresponds to a raw-data specific additional dephasing of the spins in the target region. For each image point of the magnetic resonance data set, the maximum value raw data of the corresponding image points of all raw data sets in spatial domain are selected as magnetic resonance data.

First claim

I claim as my invention:

1. A method for acquiring magnetic resonance (MR) data from a target region of an examination object, comprising:
from a control computer, operating an MR scanner, while the examination object is situated in a basic magnetic field that is produced by the MR scanner the MR scanner, to acquire a first raw MR data set and at least one further raw MR data set produced by excited nuclear spins in said target region, said target region containing at least one interfering object that has a magnetic susceptibility that differs from a remainder of said target region, which produces an interference field that degrades a homogeneity of said basic magnetic field, and thereby causes a dephasing of said nuclear spins;
from said control computer, operating said MR scanner to acquire said first MR raw data set with no dephasing other than the dephasing produced by said interference field, and to acquire said at least one further raw MR data set with additional dephasing of said nuclear spins;
from said control computer, entering raw data from said first raw MR data set and said at least one further raw MR data set into an electronic memory organized as k-space, comprising a plurality of k-space points, with each k-space point having a raw data value produced by the raw data entered thereat;
from said control computer, generating a magnetic resonance data set, comprising image points, with each image point in said magnetic resonance data set having a value that is the highest value, among the raw data values for the corresponding k-space point among the first raw MR data set and the at least one further raw MR data set; and
from said control computer, making said magnetic resonance data set available in electronic form as a data file.

2. The method as claimed in claim 1 comprising, from said control computer, operating said MR scanner to acquire said first raw MR data set and said at least one further raw MR data set in respectively different acquisition procedures, each acquisition procedure including radio-frequency excitation of said nuclear spins and in each acquisition of said at least one further raw MR data set, and producing said additional dephasing by operating said MR scanner to apply respectively different dephasing gradients in at least one direction in said target region, selected from the group consisting of a readout direction and a slice-selection direction.

3. The method as claimed in claim 1 comprising, from said control computer, operating said MR scanner to acquire said first raw MR data set and said at least one further raw MR data set in a single acquisition procedure, and producing said additional dephasing by entering said first raw MR data set and said at least one further raw MR data set from said single acquisition procedure into k-space having a size that is enlarged in at least one direction with respect to a size of k-space needed for a single raw MR data set, with said first raw MR data set and said at least one further raw MR data set occupying respectively different regions in k-space, with each region being shifted in k-space, along said at least one direction, with respect to a center of k-space.

4. The method as claimed in claim 3 comprising, from said control computer, operating said MR scanner to acquire said first raw MR data set and said at least one further raw MR data set during application of a readout gradient in a readout direction, and wherein k-space is enlarged in said readout direction by extending a time duration during which said readout gradient is applied.

5. The method as claimed in claim 1 comprising, in said control computer, determining an interference field map of said interference field by, for each image point in said magnetic resonance data set, determining an interference field value from the dephasing value for said highest raw data value.

6. The method as claimed in claim 5 comprising, from said control computer, using said interference field map to prepare a subsequent acquisition of MR data from said target region with said MR scanner.

7. The method as claimed in claim 5 comprising, from said control computer, using said interference field map in a signal-separation technique for evaluating MR data acquired using said MR scanner from protons that are bound in different compounds.

8. The method as claimed in claim 1 comprising, from said control computer, operating said MR scanner to acquire at least one additional raw MR data set from said target region with said nuclear spins being excited at a different excitation frequency compared to acquisition of said first raw MR data set and said at least one further raw MR data set.

9. The method as claimed in claim 1 comprising, in said control computer, segmenting a region produced by said examination object in each of said first raw MR data set and said at least one further raw MR data set and generating said magnetic resonance image data set using only the raw data from said first raw MR data set for regions outside of said segmented examination object.

10. The method as claimed in claim 1 comprising, in said control computer, segmenting a region produced by said examination object in said magnetic resonance image data set and, for regions outside of said segmented examination object, using only raw data from said first raw MR data set.

11. The method as claimed in claim 1 comprising, from said control computer, operating said MR scanner using a GRE sequence to acquire said first raw MR data set and said at least one further raw MR data set.

12. A magnetic resonance (MR) apparatus comprising:
an MR scanner;
a control computer configured to operate said MR scanner, while an examination object is situated in a basic magnetic field produced by the MR scanner, to acquire a first raw MR data set and at least one further raw MR data set produced by excited nuclear spins in a target region of the examination object, said target region containing at least one interfering object that has a magnetic susceptibility that differs from a remainder of said target region, which produces an interference field that degrades a homogeneity of said basic magnetic field, and thereby causes a dephasing of said nuclear spins;
said control computer being configured to operate said MR scanner to acquire said first MR raw data set with no dephasing other than the dephasing produced by said interference field, and to acquire said at least one further raw MR data set with additional dephasing of said nuclear spins;
an electronic memory organized as k-space, comprising a plurality of k-space points;
said control computer, entering raw data from said first raw MR data set and said at least one further raw MR data set into said electronic memory, with each k-space point having a raw data value produced by the raw data entered thereat;
said control computer being configured to generate a magnetic resonance data set, comprising image points, with each image point in said magnetic resonance data set having a value that is the highest value among the raw data values for the corresponding k-space point among the first raw MR data set and the at least one further raw MR data set; and
said control computer being configured to make said magnetic resonance data set available in electronic form as a data file.

Assignees

• Siemens Ag

Inventors

• Grodzki David

Classifications

• A61B5/055 Primary

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

• G01R33/4818

  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 title

• G01R33/56518

  due to eddy currents, e.g. caused by switching of the gradient magnetic field · CPC title

• G01R33/543 Primary

  Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription (G01R33/546 takes precedence) · CPC title