Magnetic resonance system and method for slice-selective detection and correction of incorrect magnetic resonance image data in slice multiplexing measurement sequences

Patent metadata

Field	Value
Publication number	US-9651640-B2
Application number	US-201213602751-A
Country	US
Kind code	B2
Filing date	Sep 4, 2012
Priority date	Sep 1, 2011
Publication date	May 16, 2017
Grant date	May 16, 2017

Abstract

In a magnetic resonance (MR) method system for slice-selective detection and correction of incorrect magnetic resonance data, a first acquisition sequence is implemented to acquire MR data from a first slice of the examination subject that is associated with a chronologically first coherence curve of the magnetization; a second acquisition sequence is implemented to acquire MR data from a second slice of the examination subject that is associated with a chronologically second coherence curve of the magnetization. In slice multiplexing measurement sequences that are characterized by the simultaneous use of the transverse magnetization of the first and second slice within the first and second acquisition sequences slice-selective errors can be detected and corrections made.

First claim

I claim as my Invention:

1. A method configured for detecting and correcting magnetic resonance (MR) image data, comprising:
with a control computer, operating an MR data acquisition unit with a first acquisition sequence in order to acquire MR data from a first slice of a subject, and in order to generate a basic magnetic field having a basic field direction, said first acquisition sequence producing a magnetization of nuclear spins in said first slice where the produced magnetization occurs in a plane that is transverse to the basic field direction and in which the produced magnetization has a phase that exhibits a phase evolution represented as a first coherence curve;
with a control computer, operating said MR data acquisition unit in order to acquire MR data from a second slice of the subject, said second acquisition sequence producing a magnetization of nuclear spins in said second slice where the produced magnetization in the second slice occurs in another plane that is transverse to the basic field direction and in which the produced magnetization has a phase that exhibits a phase evolution represented as a second coherence curve, wherein said first acquisition sequence and said second acquisition sequence are at least partially temporally overlapping so that said magnetization of said nuclear spins in said first slice and said magnetization of said nuclear spins in said second slice occur simultaneously at, at least one point in time, in which the overlapping occurs;
with a control computer, operating said MR data acquisition unit with a slice-selective correction data acquisition step in order to acquire MR signals from only said first slice, thereby obtaining correction data;
with a control computer, operating said MR data acquisition unit in order to implement at least one correction assistance step that suppresses a signal contribution of said second slice that occurs during said slice-selective correction data acquisition step, and that reestablishes said first and second coherence curves after said correction data acquisition step; and
from said control computer, making said MR data acquired from said first slice in said first acquisition sequence and said MR data acquired from said second slice from said second acquisition sequence, and said correction data, available in electronic form in order to permit further correction processing when desired.

2. A method as claimed in claim 1 comprising, in said slice-selective correction assistance step, operating said MR data acquisition unit in order to emit gradient fields that impose a correction assistance phase that then causes said second coherence curve to be dephased during said correction data acquisition step.

3. A method as claimed in claim 2 comprising generating said gradient fields with a non-linear spatial curve that makes said slice-selective correction assistance phase slice-specific for said second slice.

4. A method as claimed in claim 1 comprising, in said slice-selective correction assistance step, operating said MR data acquisition unit with a control computer, in order to radiate at least one radio-frequency pulse that imposes a slice-selective correction assistance phase by a modulation of said at least one radio-frequency pulse selected from the group consisting of amplitude modulation and phase modulation.

5. A method as claimed in claim 1 comprising with a control computer, operating said MR data acquisition unit in each of said first and second acquisition sequences in order to include an excitation step wherein said magnetization in the respective first and second slices is deflected out of an idle state, a phase modification step wherein the respective magnetization in the first and second slices is dephased and rephased, and a readout step in which a signal resulting from the respective magnetization in the first and second slices is detected within a signal detection time period.

6. A method as claimed in claim 5 comprising, in at least one of said excitation step and said phase modification step in each of said first and second acquisition sequences, radiating a radio-frequency pulse with said MR data acquisition unit.

7. A method as claimed in claim 5 comprising operating said MR data acquisition unit in order to implement said excitation step in said first acquisition sequence, and said slice-selective correction data acquisition step, before the excitation step of said second acquisition sequence.

8. A method as claimed in claim 5 comprising with a control computer, operating said MR data acquisition unit in order to implement said excitation step of said first acquisition sequence, and said slice-selective correction data acquisition step, after said excitation step of said second acquisition sequence, and in order to implement said slice-selective correction assistance step and thereby cause dephasing of said signal of said second slice before said slice-selective correction data acquisition step, and wherein said slice-selective correction assistance step rephases the respective signals from the first and second slices after said correction data acquisition step.

9. A method as claimed in claim 5 comprising with a control computer, operating said MR data acquisition unit with each of said first and second acquisition sequences being a simultaneous echo refocusing sequence, and with a control computer, implementing the respective readout steps in said respective simultaneous echo focusing sequences with a time offset in said signal detection time period.

10. A method as claimed in claim 5 comprising with a control computer, implementing the respective readout steps in said first and second acquisition sequences simultaneously within said signal detection time period.

11. A method as claimed in claim 10 comprising with a control computer, operating said MR data acquisition unit in order to implement the respective excitation steps of said first and second acquisition sequences with at least a partial temporal overlap, and differentiating respective signals from the respective first and second slices by phase or frequency.

12. A method as claimed in claim 10 comprising with a control computer, operating said MR data acquisition unit in said first and second acquisition sequences by radiating respective radio-frequency pulses from respective, multiple radio-frequency coils of said MR data acquisition unit.

13. A method as claimed in claim 10 comprising with a control computer, operating the MR data acquisition unit in order to implement the respective excitation steps of said first and second acquisition sequences with a time offset with respect to each other.

14. A method as claimed in claim 10 comprising with a control computer, operating the MR data acquisition unit in order to implement the respective phase modification steps of said first and second acquisition sequences with a time offset with respect to each other.

15. A magnetic resonance (MR) system comprising:
an MR data acquisition unit;
a control unit configured to operate said MR data acquisition unit with a first acquisition sequence in order to acquire MR data from a first slice of a subject and in order to generate a basic magnetic field having a basic field direction, said first acquisition sequence producing a magnetization of nuclear spins in said first slice where the produced magnetization occurs in a plane that is transverse to the basic field direction and in which the produced magnetization has a phase that exhibits a phase evolution represented as a first coherence curve;
said control unit being configured to operate said MR data acquisition unit in ord

Assignees

• Feiweier Thorsten
• Siemens Ag

Inventors

• Feiweier Thorsten

Classifications

• G01R33/56545

  caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts · CPC title

• A61B5/055 Primary

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

• G01R33/56581

  due to Maxwell fields, i.e. concomitant fields · CPC title

• G01R33/4835 Primary

  of multiple slices · CPC title

• G01R33/565

  Correction of image distortions, e.g. due to magnetic field inhomogeneities · CPC title