Magnetic resonance imaging with switched-mode current-source amplifier having gallium nitride field effect transistors for parallel transmission in MRI

Patent metadata

Field	Value
Publication number	US-9747789-B2
Application number	US-201314053144-A
Country	US
Kind code	B2
Filing date	Oct 14, 2013
Priority date	Mar 31, 2013
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

Example systems, apparatus, circuits, and other embodiments described herein concern parallel transmission in MRI. One example apparatus includes at least two enhanced mode gallium nitride (eGaN) based field effect transistors (FETs) that are connected by a coil that includes an LC (inductance-capacitance) leg. The apparatus includes a controller that inputs a signal to the eGaN FETs to control the production of an output analog radio frequency (RF) signal. The LC leg selectively alters the output analog RF signal. The analog RF signal is used in parallel magnetic resonance imaging (MRI) transmission. One embodiment provides an MRI transmit coil with switched-mode current-source amplification provided by a gallium nitride FET.

First claim

What is claimed is:

1. An on-coil switched-mode current-source amplifier for parallel transmission in magnetic resonance (MR), comprising:
at least two field effect transistors (FETs) connected by a coil including an LC (inductance-capacitance) leg, the at least two FETs being gallium nitride (GaN) FETs,
a class S amplifier configured to provide a source voltage to the at least two FETs,
where the coil is configured to produce an output analog radio frequency (RF) signal associated with parallel magnetic resonance imaging (MRI) transmission, and
where the output analog RF signal depends, at least in part, on a current output by the at least two FETs.

2. The on-coil switched-mode current-source amplifier of claim 1 , the at least two FETs being enhanced mode gallium nitride (eGaN) FETs.

3. The on-coil switched-mode current-source amplifier of claim 1 , where the at least two FETs drive a current in the coil of at least 3 A rms.

4. The on-coil switched-mode current-source amplifier of claim 1 , where one of the at least two FETs is less than 2 mm 2 .

5. The on-coil switched-mode current-source amplifier of claim 1 , where the amplifier is configured to be within 1 centimeter of a bore of an MR apparatus.

6. The on-coil switched-mode current-source amplifier of claim 1 , the coil being a multi-turn coil.

7. The on-coil switched-mode current-source amplifier of claim 1 , where a drain efficiency of the at least two FETs is at least 85% when driving a 50 ohm load.

8. The on-coil switched-mode current-source amplifier of claim 1 , where a power added efficiency of the at least two FETs is at least 85% when driving a 50 ohm load.

9. The on-coil switched-mode current-source amplifier of claim 1 , comprising:
an envelope elimination and restoration circuit configured to replicate shaped RF pulses produced by an MR scanner, the envelope elimination and restoration circuit connected to the on-coil switched-mode current-source amplifier.

10. The on-coil switched-mode current-source amplifier of claim 1 , where the at least two FETs drive a current in the coil of at least 5 A rms.

11. The on-coil switched-mode current-source amplifier of claim 1 , where one of the at least two FETs is less than 0.5 mm 2 .

12. The on-coil switched-mode current-source amplifier of claim 1 , where the amplifier is configured to be within 2 meters of a bore of an MR apparatus.

13. An on-coil switched-mode current-source amplifier for parallel transmission in magnetic resonance (MR), comprising:
at least two field effect transistors (FETs) connected by a coil including an LC (inductance-capacitance) leg, the at least two FETs being gallium nitride (GaN) FETs,
a class S amplifier configured to provide a source voltage to the at least two FETs, where the coil is configured to produce an output analog radio frequency (RF) signal associated with parallel magnetic resonance imaging (MRI) transmission,
a current detector that detects the current output by the coil as controlled, at least in part, by the at least two FETs, and
where the output analog RF signal depends, at least in part, on a current output by the at least two FETs.

14. The on-coil switched-mode current-source amplifier of claim 13 , the at least two FETs being enhanced mode gallium nitride (eGaN) FETs.

15. The on-coil switched-mode current-source amplifier of claim 13 , where the at least two FETs drive a current in the coil of at least 3 A rms.

16. The on-coil switched-mode current-source amplifier of claim 13 , where one of the at least two FETs is less than 2 mm 2 .

17. The on-coil switched-mode current-source amplifier of claim 13 , where the amplifier is configured to be within 1 centimeter of a bore of an MR apparatus.

18. The on-coil switched-mode current-source amplifier of claim 13 , comprising:
an envelope elimination and restoration circuit configured to replicate shaped RF pulses produced by an MR scanner, the envelope elimination and restoration circuit connected to the on-coil switched-mode current-source amplifier.

19. The on-coil switched-mode current-source amplifier of claim 13 , where the at least two FETs drive a current in the coil of at least 5 A rms.

20. The on-coil switched-mode current-source amplifier of claim 13 , where one of the at least two FETs is less than 0.5 mm 2 .

21. The on-coil switched-mode current-source amplifier of claim 13 , where the amplifier is configured to be within 2 meters of a bore of an MR apparatus.

22. An on-coil switched-mode current-source amplifier for parallel transmission in magnetic resonance (MR), comprising:
at least two field effect transistors (FETs) connected by a coil including an LC (inductance-capacitance) leg, the at least two FETs being gallium nitride (GaN) FETs,
a class S amplifier configured to provide a source voltage to the at least two FETs, where the coil is configured to produce an output analog radio frequency (RF) signal associated with parallel magnetic resonance imaging (MRI) transmission,
a current detector that detects the current output by the coil as controlled, at least in part, by the at least two FETs,
where the output analog RF signal depends, at least in part, on a current output by the at least two FETs, and
where the class S amplifier controls the source voltage provided to the at least two FETs as a function of the current detected by the current detector.

23. The on-coil switched-mode current-source amplifier of claim 22 , the at least two FETs being enhanced mode gallium nitride (eGaN) FETs.

24. The on-coil switched-mode current-source amplifier of claim 22 , where the at least two FETs drive a current in the coil of at least 3 A rms.

25. The on-coil switched-mode current-source amplifier of claim 22 , where one of the at least two FETs is less than 2 mm 2 .

26. The on-coil switched-mode current-source amplifier of claim 22 , where the amplifier is configured to be within 1 centimeter of a bore of an MR apparatus.

27. The on-coil switched-mode current-source amplifier of claim 22 , comprising:
an envelope elimination and restoration circuit configured to replicate shaped RF pulses produced by an MR scanner, the envelope elimination and restoration circuit connected to the on-coil switched-mode current-source amplifier.

28. The on-coil switched-mode current-source amplifier of claim 22 , where the at least two FETs drive a current in the coil of at least 5 A rms.

29. The on-coil switched-mode current-source amplifier of claim 22 , where one of the at least two FETs is less than 0.5 mm 2 .

30. The on-coil switched-mode current-source amplifier of claim 22 , where the amplifier is configured to be within 2 meters of a bore of an MR apparatus.

31. An on-coil switched-mode current-source amplifier for parallel transmission in magnetic resonance (MR), comprising:
at least two field effect transistors (FETs) connected by a coil including an LC (inductance-capacitance) leg, the at least two FETs being gallium nitride (GaN) FETs,
where the coil is configured to produce an output analog radio frequency (RF) signal associated with parallel magnetic resonance imaging (MRI) transmission,
where the output analog RF signal depends, at least in part, on a current output by the at least two FETs, and
where a drain efficiency of the at least two FETs is at least 85% when dri

Assignees

• Univ Case Western Reserve

Inventors

• Griswold Mark
• Twieg Michael

Classifications

• A61B5/0017

  transmitting optical signals · CPC title

• G01R33/56

  Image enhancement or correction, e.g. subtraction or averaging techniques {, e.g. improvement of signal-to-noise ratio and resolution} · CPC title

• G01R33/56366

  Perfusion imaging · CPC title

• A61B5/055

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

• G01R33/4822

  in three dimensions · CPC title