Magnetic coil power methods and apparatus
An apparatus to provide power for operating at least one gradient coil of a magnetic resonance imaging system. According to some aspects, the apparatus comprises a plurality of power terminals configured to supply different voltages of a first polarity, and a linear amplifier configured to provide at least one output to power the at least one gradient coil to produce a magnetic field in accordance with a pulse sequence, the linear amplifier configured to be powered by one or more of the plurality of power terminals, wherein the one or more of the plurality of power terminals powering the linear amplifier is selected based, at least in part, on the at least one output.
1. An apparatus for providing power to operate at least one gradient coil of a magnetic resonance imaging system, the apparatus comprising:
a linear amplifier configured to produce an output that drives the at least one gradient coil in accordance with a pulse sequence;
at least one power converter configured to produce a variable power supply voltage to power the linear amplifier; and
at least one controller configured to control the at least one power converter to change the variable power supply voltage based upon an output of the linear amplifier.
2. The apparatus of claim 1 , wherein the pulse sequence comprises a plurality of gradient pulses, and wherein the at least one controller is configured to change the variable power supply voltage in correspondence with changing power demands needed to power the at least one gradient coil in accordance with the pulse sequence.
3. The apparatus of claim 2 , wherein the at least one controller is configured to increase the variable power supply voltage in correspondence with a rising edge of each of the plurality of gradient pulses.
4. The apparatus of claim 3 , wherein the at least one controller is configured to decrease the variable power supply voltage in correspondence with a falling edge of each of the plurality of gradient pulses.
5. The apparatus of claim 1 , wherein the at least one power converter comprises a first power converter configured to produce a variable positive power supply voltage to power the linear amplifier and a second power converter configured to produce a variable negative power supply voltage to power the linear amplifier.
6. The apparatus of claim 1 , wherein the at least one power converter comprises a switching power converter.
7. The apparatus of claim 1 , wherein the output of the linear amplifier is configured to be coupled to the at least one gradient coil.
8. A method of providing power to at least one gradient coil of a magnetic resonance imaging system using a linear amplifier configured to provide current to the at least one gradient coil to produce a magnetic field in accordance with a pulse sequence, the method comprising:
converting at least one fixed power supply to at least one variable power supply voltage to power the linear amplifier;
changing the at least one variable power supply voltage based upon an output of the linear amplifier; and
controlling the linear amplifier to produce an output that drives the at least one gradient coil in accordance with the pulse sequence.
9. The method of claim 8 , wherein the pulse sequence comprises a plurality of gradient pulses, and wherein changing the at least one variable power supply voltage comprises changing the at least one variable power supply voltage in correspondence with changing power demands needed to power the at least one gradient coil in accordance with the pulse sequence.
10. The method of claim 9 , wherein changing the at least one variable power supply voltage comprises increasing the at least one variable power supply voltage in correspondence with a rising edge of each of the plurality of gradient pulses.
11. The method of claim 10 , wherein changing the at least one variable power supply voltage comprises decreasing the at least one variable power supply voltage in correspondence with a falling edge of each of the plurality of gradient pulses.
12. The method of claim 10 , wherein converting the at least one fixed power supply to at least one variable power supply voltage to power the linear amplifier comprises controlling a switching power converter.
13. The method of claim 12 , wherein controlling the switching power converter comprises controlling a switching power converter configured to switch at a switching frequency above a Larmor frequency associated with a B0 field strength of the magnetic resonance imaging system to power the at least one gradient coil in accordance with a pulse sequence.
14. The method of claim 13 , wherein controlling the switching power converter comprises controlling the switching power converter to switch at a switching frequency greater than 1 MHz and less than 10 MHz.
15. The method of claim 13 , wherein controlling the switching power converter comprises controlling the switching power converter to switch at a switching frequency greater than 10 MHz and less than 30 MHz.
16. The method of claim 13 , wherein controlling the switching power converter comprises controlling the switching power converter to switch at a switching frequency greater than 30 MHz and less than 300 MHz.
17. The method of claim 13 , wherein controlling the switching power converter comprises controlling the switching power converter to switch at a switching frequency greater than 300 MHz.
18. The method of claim 8 , wherein the output of the linear amplifier is coupled to the at least one gradient coil.
19. A magnetic resonance imaging system comprising:
a B0 magnet configured to produce a B0 magnetic field;
at least one gradient coil; and
at least one power component configured to provide power to operate the at least one gradient coil, the at least one power component comprising:
a linear amplifier configured to produce an output that drives the at least one gradient coil in accordance with a pulse sequence;
at least one power converter configured to produce a variable power supply voltage to power the linear amplifier; and
at least one controller configured to control the at least one power converter to change the variable power supply voltage based upon an output of the linear amplifier.
20. The magnetic resonance imaging system of claim 19 , wherein the B0 magnet, when operated, is configured to produce a B0 magnetic field having a field strength equal to or less than approximately 0.2 T and greater than or equal to approximately 0.1 T.
21. The magnetic resonance imaging system of claim 19 , wherein the B0 magnet, when operated, is configured to produce a B0 magnetic field having a field strength equal to or less than approximately 0.1 T and greater than or equal to approximately 50 mT.
22. The magnetic resonance imaging system of claim 19 , wherein the B0 magnet, when operated, is configured to produce a B0 magnetic field having a field strength equal to or less than approximately 50 mT and greater than or equal to approximately 20 mT.
23. The magnetic resonance imaging system of claim 19 , wherein the B0 magnet, when operated, is configured to produce a B0 magnetic field having a field strength equal to or less than approximately 20 mT and greater than or equal to approximately 10 mT.
24. The magnetic resonance imaging system of claim 19 , wherein the at least one gradient coil comprises at least one first gradient coil, at least one second gradient coil and at least one third gradient coil to provide encoding in three-dimensions, and wherein the at least one power component is configured to provide power to the at least one first gradient coil, the at least one second gradient coil and the at least one third gradient coil.
25. The magnetic resonance imaging system of claim 19 , wherein the pulse sequence comprises a plurality of gradient pulses, and wherein the at least one controller is configured to change the variable power supply voltage in correspondence with changing power demands needed to power the at least one gradient coil in accordance with the pulse sequence.
26. The magnetic resonance imaging system of claim 19 , wherein the at least one power converter comprises a first power converter configured to produce a variable positive power supply voltage to power the linear amplifier and a second power converter configured to produce a variable negative power supply voltage to power the linear amplifier.
27. The magnetic resonance imaging system of claim 26 , wherein the pulse sequence comprises a plurality of gradient pulses, and wherein the at least one controller is configured to change the variable positive power supply voltage and the variable negative power supply voltage in correspondence with changing power demands needed to power the at least one gradient coil in accordance with the pulse sequence.
28. The magnetic resonance imaging system of claim 19 , wherein the at least one power converter comprises a switching power converter.
29. The magnetic resonance imaging system of claim 19 , wherein the output of the linear amplifier is coupled to the at least one gradient coil.