Generation of rf signals for excitation of nuclei in magnetic resonance systems

Patent metadata

Field	Value
Publication number	US-2018238975-A1
Application number	US-201615753432-A
Country	US
Kind code	A1
Filing date	Aug 19, 2016
Priority date	Aug 21, 2015
Publication date	Aug 23, 2018
Grant date	—

Abstract

The invention provides for a system (200) for generation of a radio frequency, RF, excitation signal for excitation of nuclei via an RF excitation coil (114) in a magnetic resonance system (100). The system comprises power generation units (203-206) each comprising a synthesizer (211-214), an RF amplifier (231-234), and a first feedback loop (251-254) unit adapted to configure the synthesizer to generate an RF signal which after amplification by the RF amplifier has a predefined first signal characteristic and a combiner (261) adapted for combining the RF signals amplified by the RF amplifiers for obtaining the RF excitation signal.

First claim

1 . A system for generation of a radio frequency, RF, excitation signal for excitation of nuclei via an RF excitation coil in a magnetic resonance, MR, system, the system comprising:
power generation units each comprising a synthesizer, an RF amplifier, and a first feedback loop unit adapted to include a sensor to register RF signal properties at the RF amplifier's output, compare the registered RF signal properties with target RF signal properties and configure the synthesizer to generate an RF signal which after amplification by the RF amplifier has a predefined first signal characteristic a combiner adapted for combining the RF signals amplified by the RF amplifiers for obtaining the RF excitation signal and the system comprising a second feedback loop unit adapted to include a sensor to register RF signal characteristics at the combiner's output, compare the registered signal characteristic with a target signal characteristic and control the synthesizers for providing the RF signals such that the RF excitation signal has a predefined second signal characteristic.

2 . The system of claim 1 , the system further comprising:
a memory storing machine-executable instructions, a processor for controlling the system, wherein execution of the machine-executable instructions by the processor causes the system to:
receive a request to generate the specified RF excitation signal,
split the specified RF excitation signal into signal components of the RF signal,
determine, for each of the power generation units, the respective predefined first signal characteristic representing one of the signal components, and
generate the specified RF signal using the first signal characteristics.

3 . The system of claim 2 , one of the signal components having higher peak amplitude than the other signal components.

4 . The system of claim 2 , one of the signal components being allocated in a different time-frequency domain as the other signal components.

5 . The system of claim 2 , the MR system being a magnetic resonance imaging system, the specified RF excitation signal comprising composite RF signal, wherein at least one of RF pulses of the composite RF signal is constructed out of fragments of the different signal components.

6 . The system of claim 2 , the system further comprising wherein execution of the machine-executable instructions by the processor causes the system to:
determine the predefined second signal characteristic to obtain the specified RF excitation signal.

7 . The system of claim 2 , each power generation unit further comprising:
a power supply of the RF amplifier and a third feedback loop adapted to configure the power supply for supplying an electrical power to the RF amplifier with a predefined electrical power characteristic, wherein the determining, for each of the power generation units, of the respective predefined first signal characteristic comprises determining, for each of the power generation units, the respective predefined electrical power characteristic ensuring that the RF signal after the amplification has the respective first signal characteristic.

8 . The system of claim 7 , each RF amplifier comprising a field effect transistor, FET, configured for the amplification of the RF signal, the predefined electrical power characteristic comprises at least one of the following: voltage at a gate of the FET and current flowing through a channel of the FET.

9 . The system of claim 8 , the power supplies being switched power supplies each comprising a capacitor bank and a ferrite choke both being galvanically connected to a drain of the respective FET, the capacitor banks being configured for incorporation into a main magnet assembly of the MR system, the ferrite chokes being configured for being positioned remotely from the main magnet assembly of the MR system.

10 . The system of claim 2 , said predetermined signal characteristics comprising at least one of the following: average power, peak power, phase, spectrum, intermodulation, amplitude, and pulse shape.

11 . The system of any of the preceding claims, the RF amplifiers and/or combiner being adapted for being incorporated in a main magnet assembly of the MR system.

12 . A method for generating of a radio frequency, RF, excitation signal for excitation of nuclei via an RF excitation coil in a magnetic resonance, MR, system comprising:
power generation units each comprising an RF amplifier and a combiner adapted for combining the RF signals amplified by the RF amplifiers for obtaining the RF excitation signal, the method comprising:
receiving a request to generate the specified RF excitation signal,
splitting the specified RF excitation signal into signal components of the specified RF excitation signal, and
determining, for each of power generation units of the system, a respective predefined first signal characteristic representing one of the signal components, each of the power generation units further comprising a synthesizer and configuring by a first feedback loop unit the synthesizer to generate an RF signal which after amplification by the RF amplifier has the predefined first signal characteristic, combining the RF signals amplified by the RF amplifiers for obtaining the RF excitation signal and
determining a second signal characteristic of the RF excitation signal and configuring by a second feedback loop the synthesizers such that the RF excitation signal has a target second signal characteristic.

13 . A computer program product comprising machine-executable instructions for performing the method of claim 12 .

14 . A magnetic resonance, MR, system comprising:
a main magnet, one or more radio frequency, RF, coils for excitation of nuclei in the MR system by an RF excitation signal, an RF transmitter for generation of the RF excitation signal used for excitation of the nuclei via the one or more RF coils, the RF transmitter comprising:
power generation units each comprising a synthesizer, an RF amplifier and a first feedback loop unit adapted to include a sensor to register RF signal properties at the RF amplifier's output, compare the registered RF signal properties with target RF signal properties and configure the synthesizer to generate an RF signal which after amplification by the RF amplifier has a predefined first signal characteristic and
a combiner adapted for combining the RF signals amplified by the RF amplifiers for obtaining the RF excitation signal, and
the RF transmitter comprising a second feedback loop unit adapted to include a sensor to register RF signal characteristics at the combiner's output, compare the registered signal characteristic with a target signal characteristic and control the synthesizers for providing the RF signals such that the RF excitation signal has a predefined second signal characteristic, the MR system further comprising:
a memory storing machine-executable instructions,
a processor for controlling the MR system, wherein execution of the machine-executable instructions by the processor causes the MR system to:
receive a specification of the RF excitation signal,
split the specified RF excitation signal into signal components of the specified RF excitation signal,
determine, for each of the power generation units, the respective predefined first signal characteristic representing one of the signal components, and
generate by the RF transmitter the specified RF signal using the determined predefined first signal characteristics.

15 . A magnetic resonance, MR, system as claimed in claim 14 , wherein of the machine-executable instructions by the processor caus

Assignees

• Koninklijke Philips Nv

Inventors

• Leussler Christoph
• Vernickel Peter

Classifications

• G01R33/3804

  Additional hardware for cooling or heating of the magnet assembly, for housing a cooled or heated part of the magnet assembly or for temperature control of the magnet assembly · CPC title

• G01R33/3614

  RF power amplifiers · CPC title

• G01R33/3607 Primary

  RF waveform generators, e.g. frequency generators, amplitude-, frequency- or phase modulators or shifters, pulse programmers, digital to analog converters for the RF signal, means for filtering or attenuating of the RF signal · CPC title