Method/system for switched frequency ripple reduction in MRI gradient coils
First Claim
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1. A gradient coil system, comprising:
- a capacitor having a first side and a second side;
at least one gradient coil comprising a first end and a second end;
a first inductor connected to a first output end of a switched amplifier and connected to the first end of the gradient coil thereby providing a switched amplified current from the switched amplifier to the gradient coil;
a second inductor connected to the first end of the gradient coil thereby providing a second current to the gradient coil, wherein the second current is substantially out of phase with the switched amplified current; and
a transformer electrically coupling the first inductor with the second inductor, the transformer further comprising;
a primary side and a secondary side, wherein the primary side of the transformer is connected across the first inductor and wherein the first side of the capacitor is connected to a second side of the secondary side of the transformer and the second side of the capacitor is connected to a second output end of the switched amplifier.
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Abstract
A method of operating a system having a coil includes providing a switched amplified current to the coil, and adding a second current to the switched amplified current, wherein the second current is substantially out of phase with the switched amplified current such that the coil receives current with substantially no switching frequency ripple.
35 Citations
20 Claims
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1. A gradient coil system, comprising:
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a capacitor having a first side and a second side;
at least one gradient coil comprising a first end and a second end;
a first inductor connected to a first output end of a switched amplifier and connected to the first end of the gradient coil thereby providing a switched amplified current from the switched amplifier to the gradient coil;
a second inductor connected to the first end of the gradient coil thereby providing a second current to the gradient coil, wherein the second current is substantially out of phase with the switched amplified current; and
a transformer electrically coupling the first inductor with the second inductor, the transformer further comprising;
a primary side and a secondary side, wherein the primary side of the transformer is connected across the first inductor and wherein the first side of the capacitor is connected to a second side of the secondary side of the transformer and the second side of the capacitor is connected to a second output end of the switched amplifier. - View Dependent Claims (2)
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3. A method of operating a magnetic resonance imaging (MRI) system having a gradient coil, said method comprising:
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providing a switched amplified current to the gradient coil from a switched amplifier via a first inductor; and
providing a second current to the gradient coil via a second inductor, wherein the first inductor is coupled to the second inductor via a transformer with the switched amplified current and the second current being substantially out of phase and wherein the switched amplified current and the second current are obtained from the switched amplifier. - View Dependent Claims (4, 5, 6, 7, 8)
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9. A gradient coil system comprising:
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at least one gradient coil comprising a first end and a second end;
a first inductor connected to said first end and providing a switched amplified current to said gradient coil;
a second inductor connected to said first end and providing a second current to said gradient coil, the second current substantially out of phase with the switched amplified current such that said gradient coil receives current with substantially no switching frequency ripple; and
a transformer coupling the first inductor with the second inductor. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A magnetic resonance imaging (MRI) system comprising:
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a main magnet configured to generate a substantially uniform magnetic field;
a radio frequency pulse generator configured to excite the magnetic field;
a gradient coil configured to generate gradients extending in different directions in the magnetic field, said gradient coil comprising a first end and a second end;
a first inductor connected to said first end and providing a switched amplified current to said gradient coil;
a second inductor connected to said first end and providing a second current to said gradient coil, the second current substantially out of phase with the switched amplified current such that said gradient coil receives current with substantially no switching frequency ripple; and
a transformer coupling the first inductor with the second inductor. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification