Determination of a magnetic resonance system activation sequence

Patent metadata

Field	Value
Publication number	US-9562958-B2
Application number	US-201313847373-A
Country	US
Kind code	B2
Filing date	Mar 19, 2013
Priority date	Mar 20, 2012
Publication date	Feb 7, 2017
Grant date	Feb 7, 2017

Abstract

A method and a control sequence determination device for the determination of a magnetic resonance system activation sequence including at least one high-frequency pulse sequence to be transmitted by a magnetic resonance system are provided. A current B 0 map and optionally a target magnetization are acquired. In addition, a k-space trajectory type is determined. An error density is calculated in a k-space based on the current B 0 map and optionally based on the target magnetization using an analytic function. This analytic function defines an error density in the k-space as a function of the current B 0 map and optionally the target magnetization. Taking account of the error density in the k-space, a k-space trajectory of the specified k-space trajectory type is determined. The high-frequency pulse sequence is determined for the k-space trajectory in an HF pulse optimization process.

First claim

The invention claimed is:

1. A method for the determination of a magnetic resonance system activation sequence comprising at least one high-frequency pulse sequence transmitted by a magnetic resonance system, the method comprising:
acquiring a current B 0 map;
acquiring a k-space trajectory type;
calculating an error density in k-space on the basis of the current B 0 map using an analytical function that defines an error density in the k-space as a function of the current B 0 map;
determining a k-space trajectory of the acquired k-space trajectory type taking account of the error density in the k-space; and
determining the at least one high-frequency pulse sequence for the k-space trajectory in an HF pulse optimization process.

2. The method as claimed in claim 1 , further comprising acquiring a target magnetization.

3. The method as claimed in claim 2 , wherein calculating the error density comprises calculating the error density on the basis of the current B 0 map and the target magnetization.

4. The method as claimed in claim 1 , further comprising determining, on the basis of the current B 0 map, a phase error map,
wherein calculating the error density in the k-space comprises calculating the error density based on the phase error map.

5. The method as claimed in claim 1 , wherein the magnetic resonance system activation sequence comprises a multi-channel pulse sequence with a plurality of individual high frequency (HF) pulse sequences to be transmitted in parallel by the magnetic resonance system via a plurality of different independent high-frequency transmission channels.

6. The method as claimed in claim 1 , wherein determining the k-space trajectory comprises determining the k-space trajectory such that the k-space, at activation of the magnetic resonance system, is sub-sampled with the aid of the magnetic resonance system activation sequence.

7. The method as claimed in claim 6 , wherein the k-space is sub-sampled at least area by area in a regular pattern.

8. The method as claimed in claim 6 , wherein the k-space is sub-sampled at least area by area in an irregular pattern, at random, or in an irregular and random pattern.

9. The method as claimed in claim 1 , wherein determining the k-space trajectory comprises determining the k-space trajectory based on at least one examination-specific parameter, at least one device-specific parameter, or at least one examination-specific parameter and at least one device-specific parameter.

10. The method as claimed in claim 9 , wherein determining the k-space trajectory comprises determining the k-space trajectory based on the at least one device-specific parameter, and
wherein the at least one device-specific parameter comprises number of transmission channels, maximum gradient amplitude, or maximum gradient slew rate.

11. The method as claimed in claim 1 , further comprising reacquiring, during a measurement, the current B 0 map; and
redetermining, based on the reacquired current B 0 map, the k-space trajectory for the magnetic resonance system activation sequence used subsequently in the measurement.

12. A method for the operation of a magnetic resonance system, the method comprising:
determining an activation sequence comprising at least one high-frequency pulse sequence transmitted by a magnetic resonance system, the determining comprising:
acquiring a current B 0 map;
acquiring a k-space trajectory type;
calculating an error density in k-space on at least the basis of the current B 0 map using an analytical function that defines an error density in the k-space as a function of the current B 0 map;
determining a k-space trajectory of the acquired k-space trajectory type taking account of the error density in the k-space; and
determining the at least one high-frequency pulse sequence for the k-space trajectory in an HF pulse optimization process; and

operating the magnetic resonance system under the use of the determined activation sequence.

13. A control sequence determination device operable to determine a magnetic resonance system activation sequence comprising at least one high-frequency pulse sequence to be transmitted by a magnetic resonance system, the control sequence determination device comprising:
an input interface arrangement operable to acquire:
a current B 0 map;
a k-space trajectory type; and
a target magnetization;

an error density calculation unit operable to calculate an error density in a k-space based on the current B 0 map using an analytical function that defines a B 0 field error density in the k-space as a function of the current B 0 map;
a trajectory determination unit operable to determine a k-space trajectory of the acquired k-space trajectory type taking account of the B 0 field error density in the k-space; and
a high frequency (HF) pulse optimization unit operable to determine the at least one high-frequency pulse sequence for the k-space trajectory.

14. The control sequence determination device as claimed in claim 13 , wherein the error density calculation unit is operable to calculate the error density based on the target magnetization.

15. The control sequence determination device as claimed in claim 14 , wherein the analytical function defines the B 0 field error density in the k-space as a function of the target magnetization.

16. A magnetic resonance system comprising:
a high-frequency transmission device comprising a gradient system and a control unit, the high-frequency transmission device configured to:
transmit a high-frequency pulse sequence in order to carry out a desired measurement on the basis of a specified activation sequence; and
coordinated with the transmission of the high-frequency pulse sequence, transmit, via the gradient system, a gradient pulse sequence; and

a control sequence determination device operable to determine the activation sequence, the activation sequence comprising at least one high-frequency pulse sequence, and operable to transmit the activation sequence to the control unit, the control sequence determination device comprising:
an input interface arrangement operable to acquire:
a current B 0 map;
a k-space trajectory type; and
a target magnetization;

an error density calculation unit operable to calculate an error density in a k-space based on the current B 0 map using an analytical function that defines a B 0 field error density in the k-space as a function of the current B 0 map; and
a trajectory determination unit operable to determine a k-space trajectory of the acquired k-space trajectory type taking account of the B 0 field error density in the k-space; and
a high frequency (HF) pulse optimization unit operable to determine the at least one high-frequency pulse sequence for the k-space trajectory.

17. The magnetic resonance system as claimed in claim 16 , wherein the error density calculation unit is operable to calculate the error density based on the target magnetization.

18. The magnetic resonance system as claimed in claim 16 , wherein the analytical function defines the B 0 field error density in the k-space as a function of the target magnetization.

19. A computer program that is loadable directly into a non-transitory computer-readable medium of a control sequence determination device, the computer program including instructions that are executable by the control sequence determination device, the instructions comprising:
acquiring a current B 0 map;
acquiring a k-space trajectory type;
calculating an error density in k-space on

Assignees

• Siemens Ag

Inventors

• Pfeuffer Josef
• Schneider Rainer

Classifications

• G01R33/5612

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

• G01R33/56563

  caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title

• G01R33/4833 Primary

  using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices · CPC title

• G01R33/4836

  using an RF pulse being spatially selective in more than one spatial dimension, e.g. a 2D pencil-beam excitation pulse · CPC title

• G01R33/38 Primary

  Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field · CPC title