Method and system for operating a magnetic resonance facility

Patent metadata

Field	Value
Publication number	US-11035921-B2
Application number	US-201916553660-A
Country	US
Kind code	B2
Filing date	Aug 28, 2019
Priority date	Aug 28, 2018
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

In a method for operating a magnetic resonance (MR) facility during recording of MR data by using a MR sequence including a saturation module for a spin type to be saturated, in which a high-frequency saturation pulse is emitted between first and second spoiler gradient pulses, and multiple further gradient pulses apart from the spoiler gradient pulses, eddy current data is determined. The eddy current data describes eddy currents existing during emission of the saturation pulse and resulting from the further gradient pulses. Further, a pulse parameter of the first spoiler gradient pulse is selected based on the eddy current data such that the eddy currents generated by the first spoiler gradient pulse compensate for at least part of the eddy currents described by the eddy current data during emission of the saturation pulse. The facility is controlled to emit the first spoiler gradient pulse with the selected pulse parameter.

First claim

The invention claimed is:

1. A method for operating a magnetic resonance (MR) scanner during recording of magnetic resonance data by using a magnetic resonance sequence, which includes at least one saturation module for a spin type to be saturated, in which a high-frequency saturation pulse is emitted between a first and a second spoiler gradient pulse, and multiple further gradient pulses apart from the spoiler gradient pulses, the method comprising:
determining eddy current data corresponding to eddy currents which exist during emission of the saturation pulse and resulting from the further gradient pulses;
selecting at least one pulse parameter of the first spoiler gradient pulse based on the eddy current data such that the eddy currents generated by way of the first spoiler gradient pulse compensate for at least part of the eddy currents identified in the eddy current data at least during emission of the saturation pulse; and
controlling the MR scanner to emit the first spoiler gradient pulse with the at least one selected pulse parameter.

2. The method as claimed in claim 1 , wherein the pulse parameter includes pulse parameters determining a pulse shape, a polarity, or gradient directions used.

3. The method as claimed in claim 1 , wherein:
the further gradient pulses comprise at least one diffusion gradient pulse in a diffusion module of the magnetic resonance sequence.

4. The method as claimed in claim 3 , wherein, as a pulse parameter, a polarity of the first spoiler gradient pulse of the saturation module following the diffusion module is selected opposite to that of the at least one diffusion gradient pulse.

5. The method as claimed in claim 1 , wherein the eddy current data is determined:
based on a simulation using sequence data;
using a mathematical relation of the sequence data; and/or
based on the sequence data describing the further gradient pulses.

6. The method as claimed in claim 1 , wherein the eddy current data is determined based on at least one item of component information describing at least one property of at least one component of the MR scanner with reference to eddy currents induced by gradient pulses.

7. The method as claimed in claim 6 , wherein the at least one item of component information is determined in a calibration operation by measuring with predefined calibration gradient pulses.

8. The method as claimed in claim 6 , wherein the at least one item of component information comprises: at least one strength variable describing a strength of the induced eddy currents, and/or at least one time constant describing a decay of the eddy currents.

9. The method as claimed in claim 1 , wherein the at least one pulse parameter is selected such that residual eddy currents are minimized.

10. The method as claimed in claim 1 , wherein the at least one pulse parameter is selected based on at least one boundary condition.

11. The method as claimed in claim 10 , wherein the at least one boundary condition comprises:
at least one minimum overall moment of the first spoiler gradient pulse;
a maximum amplitude of the first spoiler gradient pulse; and/or
a maximum slew rate of the first spoiler gradient pulse.

12. The method as claimed in claim 10 , wherein the at least one boundary condition comprises a maximum rephasing of spins of the spin type to be saturated, that are dephased by the second spoiler gradient pulse of a preceding saturation module.

13. The method as claimed in claim 1 , further comprising adjusting, as a function of the pulse parameter selected for the first spoiler gradient pulse, at least one pulse parameter of the second spoiler gradient pulse of a preceding saturation module.

14. The method as claimed in claim 13 , wherein, in the event of a rephasing moment diverging from a specified moment due to the selected pulse parameter of the first spoiler gradient pulse, the pulse parameter of the second spoiler gradient pulse of the preceding saturation module is adjusted to generate a dephasing moment corresponding to the rephasing moment.

15. The method as claimed in claim 1 , wherein the magnetic resonance sequence is an Echo Planar Imaging (EPI) sequence.

16. A magnetic resonance (MR) system, comprising:
a MR scanner; and
a controller communicatively coupled to the MR scanner, and configured to perform the method as claimed in claim 1 .

17. A computer program product having a computer program which is directly loadable into a memory of a controller of a magnetic resonance system, when executed by the controller, causes the magnetic resonance system to perform the method as claimed in claim 1 .

18. A non-transitory computer-readable storage medium with an executable program stored thereon, that when executed, instructs a processor to perform the method of claim 1 .

19. The method as claimed in claim 1 , wherein the first spoiler gradient is configured to rephase spins of the spin type to be saturated at a start of the saturation pulse.

20. The method as claimed in claim 1 , further comprising adjusting the second spoiler gradient pulse of a preceding saturation module based on the first spoiler gradient pulse.

Assignees

• Siemens Healthcare Gmbh

Inventors

• Hoelscher Uvo
• Koehler Michael
• Niederloehner Daniel
• Stemmer Alto

Classifications

• 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

• G01R33/58

  Calibration of imaging systems, e.g. using test probes {, Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material} · CPC title

• G01R33/56341

  Diffusion imaging · CPC title

• G01R33/543

  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

• G01R33/56518 Primary

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