Method, system and magnetic resonance apparatus for compensating for inhomogeneities in the magnetic field

Patent metadata

Field	Value
Publication number	US-10488478-B2
Application number	US-201514687378-A
Country	US
Kind code	B2
Filing date	Apr 15, 2015
Priority date	Apr 16, 2014
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

A method and a magnetic resonance apparatus compensate for inhomogeneities in a magnetic field generated by the magnetic resonance apparatus with a shim coil of the magnetic resonance apparatus. The shim coil is arranged at an object under investigation. A position and an orientation of the shim coil are automatically determined. The inhomogeneities of the magnetic field are determined. The inhomogeneities are compensated for via the shim coil depending on the position and the orientation of the shim coil.

First claim

The invention claimed is:

1. A method for compensating for inhomogeneities in a magnetic field generated by a magnetic resonance apparatus with a local shim coil, the method comprising:
arranging the local shim coil at an object under investigation;
changing a positional, orientational, or positional and orientational relationship between a local coil, the local shim coil, or both the local coil and the local shim coil and a device, the device being a portion or lower shell of a housing of the local coil, wherein the device is configured to be firmly mounted on the magnetic resonance apparatus;
automatically determining a changed position, a changed orientation, or a changed position and a changed orientation of the local shim coil with respect to the device based on the changed positional, changed orientational, or changed positional and changed orientational relationship between the local coil, the local shim coil, or both the local coil and the local shim coil and the device;
determining the inhomogeneities of the magnetic field; and
compensating for the inhomogeneities via the local shim coil depending on the changed position, the changed orientation, or the changed position and the changed orientation of the local shim coil.

2. The method of claim 1 , wherein automatically determining the changed position, the changed orientation, or the changed position and the changed orientation of the local shim coil comprises automatically communicating the changed position, the changed orientation, or the changed position and the changed orientation of the local shim coil to the magnetic resonance apparatus.

3. The method of claim 2 , wherein automatically communicating the changed position, the changed orientation, or the changed position and the changed orientation is implemented via an interrupt message, a coil code, or both the interrupted message and the coil code.

4. The method of claim 1 , wherein:
a finite number of combinations of the changed position, the changed orientation, or the changed position and the changed orientation of the local shim coil are provided;
for each combination of the finite number of combinations, an item of information exists regarding how the magnetic field changes depending on a current flowing through the local shim coil; and
compensating for the inhomogeneities is implemented depending on the item of information corresponding with the determined changed position, changed orientation, or changed position and changed orientation of the local shim coil.

5. The method of claim 1 , further comprising:
determining, for a respective changed position or for a respective changed orientation of the local shim coil, a respective item of information by measuring the magnetic field as to how the magnetic field changes depending on a current flowing through the local shim coil;
calculating, based on the determined information for the automatically determined changed position or changed orientation of the local shim coil, an item of information as to how the magnetic field changes depending on a current flowing through the local shim coil; and
compensating for the inhomogeneities is implemented depending on the calculated information.

6. A method for compensating for inhomogeneities in a magnetic field generated by a magnetic resonance apparatus, with a local shim coil, the method comprising:
changing a positional, orientational, or positional and orientational relationship between a local coil, the local shim coil, or both the local coil and the local shim coil and a device, the device being a portion or lower shell of a housing of the local coil, wherein the device is configured to be firmly mounted on the magnetic resonance apparatus;
determining the inhomogeneities of the magnetic field; and
determining an optimum position and an optimum orientation of the local shim coil in order to compensate for the inhomogeneities of the magnetic field with the local shim coil in the optimum position and with the optimum orientation in a manner better than if the local shim coil is disposed at another position or in another orientation with respect to the device.

7. The method of claim 6 , wherein:
a finite set of combinations of position and orientation of the local shim coil exists;
for each combination of the finite set of combinations, information exists as to how the magnetic field changes depending on a current flowing through the local shim coil; and
determining the optimum position and the optimum orientation comprises determining the optimum position and the optimum orientation within the set of combinations.

8. The method of claim 6 , further comprising:
determining, for at least one combination of a respective position and a respective orientation of the local shim coil, at least one item of information by measuring the magnetic field as to how the magnetic field changes depending on a current flowing through the local shim coil;
wherein determining the optimum position and the optimum orientation of the local shim coil comprises calculating the optimum position and the optimum orientation of the local shim coil starting from the at least one determined item of information.

9. A system for a magnetic resonance apparatus, the system comprising:
a local coil;
a local shim coil; and
a device;
wherein:
the device is a portion or lower shell of a housing of the local coil, and wherein the device is configured to be firmly mounted on the magnetic resonance apparatus; and
the system is configured to:
arrange the local shim coil at an object under investigation;
change a positional, orientational, or positional and orientational relationship between the local coil, the local shim coil, or both the local coil and the local shim coil and the device;
automatically determine a changed position, a changed orientation, or a changed position and a changed orientation of the local shim coil based on the changed positional, changed orientational, or changed positional and changed orientational relationship between the local coil, the local shim coil, or both the local coil and the local shim coil and the device;
determine inhomogeneities of the magnetic field; and
compensate for the inhomogeneities of the magnetic field via the local shim coil depending on the changed positional, the changed orientational, or the changed positional and the changed orientational relationship between the local coil, the local shim coil, or both the local coil and the local shim coil and the device.

10. The system of claim 9 , wherein the changed positional and changed orientational relationship between the local shim coil and the device is detectable by the magnetic resonance apparatus.

11. The system of claim 9 , wherein a finite number of changed positional and changed orientational relationships exist between the local coil, the local shim coil, or both the local coil and the local shim coil.

12. The system of claim 9 , wherein the system is configured such that the changed positional, the changed orientational, or the changed positional and the changed orientational relationship is defined only by a tilt angle through which the local coil, the local shim coil, or both the local coil and the local shim coil is tiltable relative to the device.

13. A magnetic resonance apparatus for generating a magnetic field and for compensating for inhomogeneities in the magnetic field with a local shim coil of the magnetic resonance apparatus, the magnetic resonance apparatus comprising:
a main field magnet;
a gradient field system;
at least one RF antenna; and
a control device configured to control the gradient field system and the at least on

Assignees

• Biber Stephan
• Driemel Daniel
• Hesels Katharina
• Ladeback Ralf
• Rothard Joerg
• Siemens Ag

Inventors

• Biber Stephan
• Driemel Daniel
• Hesels Katharina
• Ladeback Ralf
• Rothard Jörg

Classifications

• G01R33/3875 Primary

  using correction coil assemblies, e.g. active shimming · CPC title

• G01R33/34046

  Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils · CPC title