Emission of high frequency pulses in a magnetic resonance tomography system

Patent metadata

Field	Value
Publication number	US-10145918-B2
Application number	US-201313784797-A
Country	US
Kind code	B2
Filing date	Mar 4, 2013
Priority date	Mar 5, 2012
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

A method for emitting a sequence of high frequency pulses that may have different envelopes in a magnetic resonance tomography system is provided. A digital instruction signal that specifies the envelope for the high frequency pulses that are to be emitted is received. A digital control signal is transmitted to a high frequency unit for generating high frequency pulses, depending on the instruction signal. A test signal that allows notification of a current overload situation is received. The current control signal is reduced if the test signal indicates an overload situation.

First claim

The invention claimed is:

1. A method for emitting a sequence of high frequency pulses having different envelopes in a magnetic resonance tomography system, the method comprising:
receiving a digital instruction signal that specifies an envelope for a high frequency pulse that is to be emitted;
emitting a digital control signal to a high frequency unit for generating the high frequency pulse depending on the digital instruction signal;
receiving a test signal that allows notification to be given of a current overload situation;
calculating a standardized overload factor from the test signal, the calculating comprising dividing the test signal by a test value, wherein an overload occurs when the test signal exceeds the test value, such that a value of “1” is assigned to reaching of an overload limit; and
reducing a current control signal when the test signal indicates the current overload situation, wherein the test signal indicates the current overload situation when the standardized overload factor exceeds the value of “1.”

2. The method as claimed in claim 1 , wherein the reduction in the current control signal is achieved such that a current digital instruction signal is divided by a current value for the standardized overload factor.

3. The method as claimed in claim 1 , further comprising determining a maximum value for the standardized overload factor via at least a first pulse.

4. The method as claimed in claim 3 , further comprising:
determining a standardized maximum permissible instruction amplitude for a subsequent pulse, wherein the standardized maximum permissible instruction amplitude indicates a maximum voltage of an instruction voltage of the subsequent pulse; and
reducing the standardized maximum permissible instruction amplitude when the maximum value for the standardized overload factor is greater than “1.”

5. The method as claimed in claim 4 , wherein the determining of the maximum permissible instruction amplitude comprises dividing the maximum permissible instruction amplitude by the maximum value for the standardized overload factor.

6. The method as claimed in claim 1 , further comprising:
storing scaling factors for specified overload factors in a table; and
reducing a current instruction amplitude, the reducing of the current instruction amplitude comprising multiplying the current instruction amplitude for the current standardized overload factor by a scaling factor.

7. The method as claimed in claim 6 , further comprising determining a minimum scaling factor via at least a first pulse.

8. The method as claimed in claim 7 , further comprising:
determining a standardized maximum permissible instruction amplitude for a subsequent pulse, wherein the standardized maximum permissible instruction amplitude indicates a maximum voltage of an instruction voltage of the subsequent pulse; and
reducing the standardized maximum permissible instruction amplitude when the minimum scaling factor detected is lower than “1,” wherein the detected minimum scaling factor is based on a current scaling factor corresponding to a current overload factor.

9. The method as claimed in claim 8 , wherein the determining of the maximum permissible instruction amplitude comprises multiplying the maximum permissible instruction amplitude by the minimum scaling factor.

10. The method as claimed in claim 2 , further comprising determining a maximum value for the standardized overload factor via at least a first pulse.

11. A method for regulating a high frequency signal in a magnetic resonance tomography system, the method comprising:
emitting a sequence of high frequency pulses having different envelopes in a magnetic resonance tomography system, the emitting comprising:
receiving a digital instruction signal that specifies an envelope for a high frequency pulse that is to be emitted;
emitting a digital control signal to a high frequency unit for generating the high frequency pulse depending on the digital instruction signal;
receiving a test signal that allows notification to be given of a current overload situation;
calculating a standardized overload factor from the test signal, the calculating comprising dividing the test signal by a test value, wherein an overload occurs when the test signal exceeds the test value, such that a value of “1” is assigned to reaching of an overload limit; and
reducing a current control signal when the test signal indicates the current overload situation, wherein the test signal indicates the current overload situation when the standardized overload factor exceeds the value of “1,”

wherein a reduction in a maximum permissible instruction amplitude of a subsequent pulse in the sequence of high frequency pulses is compensated by increasing a feedback signal in a control loop of the magnetic resonance tomography system or by reducing a controller input signal in the control loop of the magnetic resonance tomography system, and wherein the maximum permissible instruction amplitude indicates a maximum voltage of an instruction voltage of the subsequent pulse.

12. The method as claimed in claim 11 , further comprising wherein increasing the feedback signal in the control loop is in proportion to the reduction in the maximum permissible instruction amplitude.

13. The method as claimed in claim 11 , wherein reducing the controller input signal is in proportion to the reduction in the maximum permissible instruction amplitude.

14. A circuit arrangement for emitting a sequence of high frequency pulses in a magnetic resonance tomography system, the circuit arrangement comprising:
a receiver unit operable to receive a digital instruction signal that specifies the envelope for the high frequency pulse to be emitted;
an output unit operable to output a digital control signal to a high frequency unit for the generation of the high frequency pulse depending on the digital instruction signal;
a test receiver operable to receive a test signal that allows notification of a current overload situation to be given;
a calculation unit operable to calculate a standardized overload factor from the test signal, the calculation comprising division of the test signal by a test value, wherein an overload occurs when the test signal exceeds the test value, such that a value of “1” is assigned to reaching of an overload limit; and
a correction unit operable to reduce a current digital control signal when the test signal indicates an overload situation, wherein the test signal indicates the current overload situation when the standardized overload factor exceeds the value of “1.”

15. A magnetic resonance tomography system comprising:
a circuit arrangement for emitting a sequence of high frequency pulses, the circuit arrangement comprising:
a receiver unit operable to receive a digital instruction signal that specifies the envelope for the high frequency pulse to be emitted;
an output unit operable to output a digital control signal to a high frequency unit for the generation of the high frequency pulse depending on the digital instruction signal;
a test receiver operable to receive a test signal that allows notification of a current overload situation to be given;
a calculation unit operable to calculate a standardized overload factor from the test signal, the calculation comprising division of the test signal by a test value, wherein an overload occurs when the test signal exceeds the test value, such that a value of “1” is assigned to reaching of an overload limit; and
a correction unit operable to reduce a current digital control signal when the test signal indicates an overload situation,

Assignees

• Demharter Nikolaus
• Huber Klaus
• Seisenberger Claus
• Speckner Thorsten
• Vester Markus
• Wuensch Christian
• Siemens Ag

Inventors

• Demharter Nikolaus
• Huber Klaus
• Seisenberger Claus
• Speckner Thorsten
• Vester Markus
• WüNSCH CHRISTIAN

Classifications

• G01R33/3614

  RF power amplifiers · CPC title

• G01R33/543 Primary

  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