Establishing B1-maps

Patent metadata

Field	Value
Publication number	US-9714996-B2
Application number	US-201414481696-A
Country	US
Kind code	B2
Filing date	Sep 9, 2014
Priority date	Sep 11, 2013
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

The embodiments relate to a B 1 -map establishment system for establishing B 1 -maps, operating using a method including: establishing a number of relative B 1 -maps and storing the relative B 1 -maps for subsequent, in particular repeated use. The B 1 -maps are used in a method for establishing an actuation sequence including: establishing a quantitative B 1 -map. establishing normalized B 1 -maps on the basis of the relative B 1 -maps and the quantitative B 1 -map, and establishing an actuation sequence or acquiring magnetic resonance measurement data using the normalized B 1 -maps. Furthermore, the embodiments relate to an actuation sequence establishment system and a magnetic resonance imaging system including such an actuation sequence establishment system.

First claim

The invention claimed is:

1. A method for establishing B 1 -maps for establishing an actuation sequence for a magnetic resonance imaging system comprising a number of transmission channels used for generating a radiofrequency field for magnetic resonance excitation of an examination object, the method comprising:
emitting a first radiofrequency field using a first transmission channel;
acquiring first radiofrequency field measurement values for the emitted first radiofrequency field;
creating a first relative B 1 -map based on the first radiofrequency field measurement values from the first transmission channel;
emitting a further radiofrequency field using a further transmission channel;
acquiring further radiofrequency field measurement values for the emitted further radiofrequency field of the further transmission channel;
creating an additional relative B 1 -map based on the further radiofrequency field measurement values from the further transmission channel;
repeating, for a number of transmission channels, the emitting of a further radiofrequency field, the acquiring of further radiofrequency field measurement values, and the creating an additional relative B 1 -map; and
storing the generated relative B 1 -maps for multiple use.

2. The method as claimed in claim 1 , further comprising:
establishing a quantitative B 1 -map;
establishing normalized B 1 -maps based on the relative B 1 -maps and the quantitative B 1 -map; and
establishing an actuation sequence for acquiring magnetic resonance measurement data using the normalized B 1 -maps.

3. The method as claimed in claim 2 , wherein a number of generated relative B 1 -maps corresponds at least to a number of transmission channels for generating a radiofrequency field in a measurement space of the magnetic resonance imaging system used for acquiring raw magnetic resonance data.

4. The method as claimed in claim 2 , further comprising:
establishing a further quantitative B 1 -map;
establishing further normalized B 1 -maps based on the stored relative B 1 -maps and the further quantitative B 1 -map; and
establishing a further actuation sequence for acquiring further magnetic resonance measurement data using the further normalized B 1 -maps.

5. The method as claimed in claim 4 , wherein a number of generated relative B 1 -maps corresponds at least to a number of transmission channels for generating a radiofrequency field in a measurement space of the magnetic resonance imaging system used for acquiring raw magnetic resonance data.

6. The method as claimed in claim 4 , wherein the quantitative B 1 -map, the further quantitative B 1 -map, or the quantitative B 1 -map and the further quantitative B 1 -map are generated using a combination of a plurality of transmission channels of the magnetic resonance imaging system.

7. The method as claimed in claim 2 , wherein at least one relative B 1 -map is generated using a combination of a plurality of transmission channels of the magnetic resonance imaging system.

8. The method as claimed in claim 7 , wherein the quantitative B 1 -map, the further quantitative B 1 -map, or the quantitative B 1 -map and the further quantitative B 1 -map are generated using a combination of the plurality of transmission channels of the magnetic resonance imaging system.

9. The method as claimed claim 8 , wherein at least two transmission channels of a combination of transmission channels used for generating the quantitative B 1 -map are contained in a combination of transmission channels used for generating at least one of the relative B 1 -maps.

10. The method as claimed in claim 7 , wherein each relative B 1 -map of the number of relative B 1 -maps is generated using a combination of the plurality of transmission channels of the magnetic resonance imaging system.

11. The method as claimed in claim 10 , wherein the quantitative B 1 -map, the further quantitative B 1 -map, or the quantitative B 1 -map and the further quantitative B 1 -map are generated using a combination of the plurality of transmission channels of the magnetic resonance imaging system.

12. The method as claimed claim 11 , wherein at least two transmission channels of a combination of transmission channels used for generating the quantitative B 1 -map are contained in a combination of transmission channels used for generating at least one of the relative B 1 -maps.

13. The method as claimed in claim 2 , wherein the quantitative B 1 -map is determined taking into account a predetermined quality criterion, wherein the predetermined quality criterion is a spatial resolution, a measurement error when determining the qualitative B1-map, or the spatial resolution and the measurement error when determining the quantitative B 1 -map.

14. The method as claimed in claim 2 , wherein there is a comparison between a quality criterion for relative B 1 -maps and a quality criterion for quantitative B 1 -maps, wherein the number of relative B 1 -maps is established based on the comparison.

15. A method for operating a magnetic resonance system, the method comprising:
establishing an actuation sequence for a magnetic resonance imaging system comprising:
(1) establishing a number of relative B 1 -maps comprising:
emitting a first radiofrequency field using a first transmission channel;
acquiring first radiofrequency field measurement values for the emitted first radiofrequency field;
creating a first relative B 1 -map based on the first radiofrequency field measurement values from the first transmission channel;
emitting a further radiofrequency field using a further transmission channel;
acquiring further radiofrequency field measurement values for the emitted further radiofrequency field of the further transmission channel;
creating an additional relative B 1 -map based on the further radiofrequency field measurement values from the further transmission channel;
repeating, for a number of transmission channels, the emitting of a further radiofrequency field, the acquiring of further radiofrequency field measurement values, and the creating an additional relative B 1 -map; and
storing the generated relative B 1 -maps for multiple use;

(2) establishing a quantitative B 1 -map;
(3) establishing normalized B 1 -maps based on the relative B 1 -maps and the quantitative B 1 -map; and
(4) establishing an actuation sequence for acquiring magnetic resonance measurement data using the normalized B 1 -maps; and

operating the magnetic resonance system using the actuation sequence.

16. A B 1 -map establishment system comprising:
an input interface configured to acquire first radiofrequency field measurement values;
a B 1 -map establishment module configured to establish a first quantitative B 1 -map based on the first radiofrequency field measurement values;
a memory module configured to repeatedly recall relative B 1 -maps from a memory module; and
a B 1 -map normalization module configured to establish a number of normalized first B 1 -maps using the relative first B 1 -maps recalled from the memory module and the first quantitative B 1 -map.

17. The B 1 -map establishment system as claimed in claim 16 , further comprising:
a quality criterion interface configured to predetermine a quality criterion.

18. An actuation sequence establishment system comprising:
a B 1 -map establishment system comprising:
an input interface configured to acquire first radiofrequency field measurement values;
a B 1 -map establishment module configured to establish a first quantitative B 1 -map based on the first radio

Assignees

• Schmidt Andreas
• Speckner Thorsten
• Sukkau Johann
• Wullenweber Michael
• Siemens Ag

Inventors

• Schmidt Andreas
• Speckner Thorsten
• Sukkau Johann
• Wullenweber Michael

Classifications

• A61B5/055

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

• G01R33/246 Primary

  Spatial mapping of the RF magnetic field B1 · CPC title

• G01R33/5612

  Parallel RF transmission, i.e. RF pulse transmission using a plurality of independent transmission channels · CPC title

• G01R33/5659

  caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title

• G01R33/54 Primary

  Signal processing systems, e.g. using pulse sequences {; Generation or control of pulse sequences; Operator console} · CPC title