Method and magnetic resonance system for distortion correction in magnetic resonance imaging

Patent metadata

Field	Value
Publication number	US-9341694-B2
Application number	US-201213491854-A
Country	US
Kind code	B2
Filing date	Jun 8, 2012
Priority date	Jun 8, 2011
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

In a method for distortion correction in spiral magnetic resonance imaging, a first MR data set is acquired by scanning raw data space along a spiral trajectory beginning at a first point. A first complex MR image is determined from the first MR data set, which includes first phase information for image points of the first MR image. A second MR data set is acquired by scanning raw data space along the spiral trajectory beginning at a second point that differs from the first point. A second complex MR image is determined from the second MR data set, which includes second phase information for image points of the second MR image. A geometric distortion for image points of the first or second MR image is determined from the first and second phase information, for example with a PLACE method.

First claim

I claim as my invention:

1. A method for correcting distortion in spiral magnetic resonance imaging wherein raw magnetic resonance data are acquired with modulation of at least two gradients respectively in two spatial directions comprising:
in a computer, automatically entering a first magnetic resonance raw data set, acquired after a single radio-frequency excitation, into k-space along a spiral trajectory in k-space, beginning at a first point of k-space;
in said computer, automatically determining a first complex MR image from said first MR raw data set, said first complex MR image comprising first phase information for respective image points of said first MR image;
in said computer, automatically entering a second MR raw data set, also acquired after a single radio-frequency excitation, into k-space along said spiral trajectory, beginning at a second point of k-space along said spiral trajectory that differs from said first point;
in said computer, automatically determining a second complex MR image from said second MR raw data set, said second complex MR image comprising second phase information for respective image points of said second MR image;
in said computer, automatically determining a geometric distortion for respective image points of said first MR image or said second MR image from said first and second phase information; and
in said computer, automatically correcting said geometric distortion in said first MR image or in said second MR image, to produce at least one corrected MR image, and making said at least one corrected MR image available in electronic form at an output of said computer, as a data file.

2. The method as claimed in claim 1 comprising entering said first and second MR raw data sets into k-space along said spiral trajectory with a predetermined radius that decreases along said spiral trajectory.

3. The method as claimed in claim 1 comprising entering said first and second MR raw data sets into k-space along said spiral trajectory with a predetermined radius that increases along said spiral trajectory.

4. The method as claimed in claim 1 comprising entering said first and second MR raw data sets into k-space with a variable speed.

5. The method as claimed in claim 1 comprising entering said first and second MR raw data sets into k-space with a variable density.

6. The method as claimed in claim 1 comprising determining said geometric distortion by using a PLACE method to generate at least one of a field map and a displacement map.

7. A method for correcting distortion in radial magnetic resonance imaging wherein raw magnetic resonance data are acquired with modulation of at least two readout gradients respectively in two spatial directions comprising:
in a computer, automatically entering a first magnetic resonance raw data set, acquired after a single radio-frequency excitation, into k-space along multiple radial trajectories in k-space respectively proceeding at different angles through a center of k-space, beginning at a first point of k-space;
in said computer, automatically determining a first complex MR image from said first MR raw data set, said first complex MR image comprising first phase information for respective image points of said first MR image;
in said computer, automatically entering a second MR raw data set, also acquired after a single radio-frequency excitation, into k-space along said radial trajectories, beginning at a second point of k-space along each radial trajectory that differs from said first point;
in said computer, automatically determining a second complex MR image from said second MR raw data set, said second complex MR image comprising second phase information for respective image points of said second MR image;
in said computer, automatically determining a geometric distortion for respective image points of said first MR image or said second MR image from said first and second phase information; and
in said computer, automatically correcting said geometric distortion in said first MR image or in said second MR image, to produce at least one corrected MR image, and making said at least one corrected MR image available in electronic form at an output of said computer, as a data file.

8. The method as claimed in claim 7 comprising entering said first and second MR raw data sets into k-space with a variable speed.

9. The method as claimed in claim 7 comprising entering said first and second MR raw data sets into k-space with a variable density.

10. The method as claimed in claim 7 comprising determining said geometric distortion by using a PLACE method to generate at least one of a field map and a displacement map.

11. A method for correcting distortion in echo planar magnetic resonance imaging wherein raw magnetic resonance data are acquired modulation of a readout gradient and a phase-coding gradient respectively in different spatial directions, comprising:
operating a magnetic resonance data acquisition unit, while an examination subject is situated therein, to acquire a first magnetic resonance raw data set following a single radio-frequency excitation of nuclear spins in the subject, and to acquire a second magnetic resonance raw data set following a single excitation of nuclear spins in the subject;
operating the magnetic resonance data acquisition unit to delay a beginning of modulation of the readout gradient and the phase-coding gradient in the acquisition of said second magnetic resonance raw data set, after the single radio-frequency excitation after which said second magnetic resonance raw data set is acquired;
in a computer, automatically entering a first magnetic resonance raw data set in k-space along said predetermined trajectory into k-space, beginning at a first point of k-space;
in said computer, automatically determining a first complex MR image from said first MR raw data set, said first complex MR image comprising first phase information for respective image points of said first MR image;
in said computer, automatically determining entering a second MR raw data set into k-space along said predetermined trajectory, beginning at a second point of k-space along said predetermined trajectory that differs from said first point;
operating said magnetic resonance data acquisition unit with said delay to cause points of said predetermined trajectory to be scanned at same points in time relative to the respective radio-frequency excitation in the acquisition of said second magnetic resonance raw data set as corresponding points of said predetermined trajectory in the acquisition of the first magnetic resonance raw data set;
in said computer, automatically determining a second complex MR image from said second MR raw data set, said second complex MR image comprising second phase information for respective image points of said second MR image;
in said computer, automatically determining a geometric distortion for respective image points of said first MR image or said second MR image from said first and second phase information; and
in said computer, automatically correcting said geometric distortion in said first MR image or in said second MR image, to produce at least one corrected MR image, and making said at least one corrected MR image available in electronic form at an output of said computer, as a data file.

12. The method as claimed in claim 11 comprising determining said geometric distortion by using a PLACE method to generate at least one of a field map and a displacement map.

13. A method for correcting distortion in echo planar magnetic resonance imaging comprising:
operating a magnetic resonance data acquisition unit to acquire first and second sets

Assignees

• Pfeuffer Josef
• Siemens Ag

Inventors

• Pfeuffer Josef

Classifications

• G01R33/56554

  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

• G01R33/5616

  using gradient refocusing, e.g. EPI · CPC title

• G01R33/4824

  using a non-Cartesian trajectory · CPC title

• A61B5/055

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

• G01R33/56572 Primary

  caused by a distortion of a gradient magnetic field, e.g. non-linearity of a gradient magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title