MAGNETIC RESONANCE IMAGING SYSTEM WITH A CLASS-E RADIO FREQUENCY AMPLIFIER
First Claim
1. A radio frequency section, for a magnetic resonance imaging system in which a control signal defines an intensity for a radio frequency excitation signal, the radio frequency section comprising:
- an exciter which produces a radio frequency carrier signal;
a Class-E amplifier that in response to the radio frequency carrier signal and the control signal produces the radio frequency excitation signal; and
a transmit coil for placement around a person being scanned by the magnetic resonance imaging system wherein the transmit coil is connected to the Class-E amplifier to receive the radio frequency excitation signal.
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Accused Products
Abstract
A Class-E amplifier has bee adapted for use in the radio frequency section of a magnetic resonance imaging (MRI) system. A drive signal is produces by modulating the envelope of a radio frequency carrier signal and then applied to a switch in the Class-E amplifier. The switch is connected in series with a choke between a supply voltage terminal and circuit ground with an output node formed between the choke and the switch. The output node is coupled to circuit ground by a shunt capacitor. In a preferred embodiment, a pair of such amplifiers, that are Π radians out of phase, are connected to each rung of a transverse electromagnetic transmit array type radio frequency coil of the MRI system.
34 Citations
32 Claims
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1. A radio frequency section, for a magnetic resonance imaging system in which a control signal defines an intensity for a radio frequency excitation signal, the radio frequency section comprising:
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an exciter which produces a radio frequency carrier signal;
a Class-E amplifier that in response to the radio frequency carrier signal and the control signal produces the radio frequency excitation signal; and
a transmit coil for placement around a person being scanned by the magnetic resonance imaging system wherein the transmit coil is connected to the Class-E amplifier to receive the radio frequency excitation signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A radio frequency section, for a magnetic resonance imaging system in which a control signal defines an intensity for a radio frequency excitation signal, the radio frequency section comprising:
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a transmit coil having a plurality of rungs;
an exciter which produces a radio frequency carrier signal;
a drive circuit that receives the control signal and the radio frequency carrier signal and produces a drive signal;
a power splitter connected to the drive circuit and dividing the drive signal into a plurality of sub-drive signals, one of which for each rung of the transmit coil;
a phase shifter for shifting phases of at least some of the sub-drive signals; and
a plurality of Class-E amplifiers, each one responding one of the plurality of sub-drive signals by producing a radio frequency excitation signal that is applied to one of the plurality of rungs of the transmit coil. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A magnetic resonance imaging system in which a control signal is produced that defines an intensity for an excitation signal, the magnetic resonance imaging system comprising:
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at least one Class-E amplifier having a choke and a switch connected in series between a supply voltage source and circuit ground with an amplifier output node formed between choke and the switch, a shunt capacitor connected in parallel with the switch, wherein the switch makes a transition from a non-conductive state to a conductive state when voltage across the switch and a derivative of the voltage across the switch both are zero; and
a coil for placement around a person being scanned by the magnetic resonance imaging system and connected to the amplifier output node. - View Dependent Claims (28, 29)
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30. A magnetic resonance system in which a control signal is produced that defines an intensity for an excitation signal, the magnetic resonance system comprising:
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at least one Class-E amplifier having a choke and a switch connected in series between a supply voltage source and circuit ground with an amplifier output node formed between choke and the switch, a shunt capacitor connected in parallel with the switch, wherein the switch makes a transition from a non-conductive state to a conductive state when voltage across the switch and a derivative of the voltage across the switch both are substantially zero; and
a transmit coil connected to the amplifier output node. - View Dependent Claims (31, 32)
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Specification