US5105153A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gradient speed-up circuit for nmr system
Assignee: General Electric Co
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Filing: 1990-06-04
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Granted: 1992-04-14
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Expires: 2010-06-04
Abstract
Abstract A gradient current speed-up circuit, for use in a higher-speed NMR imaging system having an associated gradient coil, has a gradient power amplifier receiving an input analog signal controlling the current in an amplifier output circuit connected in series between first and second portions of a single gradient coil. Semiconductor switching elements selectively connect the coil portion-amplifier-coil portion between first and second potential sources, and are turned on and off in selected patterns to cause a current to be suddenly applied to, and removed from, flow through the associated gradient coil and the amplifier output circuit.
Inventors
- 👤 Otward M. Mueller
- 👤 Peter B. Roemer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:42
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/385; G01R33/3852
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
136 words
A gradient speed-up circuit, for use in a high-speed NMR imaging system, comprising: a gradient power amplifier means for creating an output signal which is linearly related to a received control signal for controlling a current flowing through an output circuit; a gradient coil having at least one portion series connected to said amplifier output circuit; a high voltage power supply being series coupled to the gradient power amplifier means and gradient coil; and a power switching means being a full-bridge circuit for connecting the high voltage power supply in series with the gradient power amplifier means and the gradient coil, causing a current flow from the high voltage power supply through the gradient power amplifier means, and the gradient coil to change the gradient coil current, the power switching means being responsive to control signals.
Claim 2
Dependent Claim
136 words
A gradient speed-up circuit, for use in a high-speed NMR imaging system, comprising: a gradient power amplifier means for creating an output signal which is linearly related to a received control signal for controlling a current flowing through an output circuit; a gradient coil having at least one portion series connected to said amplifier output circuit; a high voltage power supply being series coupled to the gradient power amplifier means and gradient coil; and a power switching means being a full-bridge circuit for connecting the high voltage power supply in series with the gradient power amplifier means and the gradient coil, causing a current flow from the high voltage power supply through the gradient power amplifier means, and the gradient coil to change the gradient coil current, the power switching means being responsive to control signals.
Claim 3
Dependent Claim
18 words
The circuit of claim 1, further comprising means for protecting said amplifier output circuit from excessive voltage thereacross.
Claim 4
Dependent Claim
16 words
The circuit of claim 1, wherein the amplifier means causes a DC shimming current to flow.
Claim 5
Dependent Claim
18 words
The circuit of claim 1, wherein the amplifier means is connected between said first and second coil portions.
Claim 6
Dependent Claim
18 words
The circuit of claim 1, wherein said power switching means includes a plurality of individually-controllable semiconductor switching devices.
Claim 7
Dependent Claim
41 words
The circuit of claim 1, wherein said power switching means includes a plurality of individually-controllable semiconductor switching devices selected from the group consisting of gate turn-on thyristors (GTOs), insulated gate Bipolar transistors (IGBTs), and metal oxide semiconductor field effect transistors (MOSFETs).
Claim 8
Dependent Claim
16 words
The circuit of claim 6, wherein each device is connected in parallel with a reverse-conduction element.
Claim 9
Dependent Claim
99 words
A gradient speed-up circuit, for use in a high-speed NMR imaging system, comprising: gradient power amplifier means for controlling a current flowing through an output circuit, responsive to an input signal; a gradient coil having separate first and second portions, each series connected to an opposite end of said amplifier output circuit, said amplifier means adapted to cause a shim current to flow through both portions of said gradient coil; and power switching means for providing a current flow through the series circuit of said amplifier means and coil portions to change the coil current responsive to control signals.
Claim 10
Dependent Claim
99 words
A gradient speed-up circuit, for use in a high-speed NMR imaging system, comprising: gradient power amplifier means for controlling a current flowing through an output circuit, responsive to an input signal; a gradient coil having separate first and second portions, each series connected to an opposite end of said amplifier output circuit, said amplifier means adapted to cause a shim current to flow through both portions of said gradient coil; and power switching means for providing a current flow through the series circuit of said amplifier means and coil portions to change the coil current responsive to control signals.
Claim 11
Dependent Claim
122 words
A gradient speed-up circuit, for use in a high-speed NMR imaging system, comprising: gradient power amplifier means for controlling a current flowing through an output circuit, responsive to an input signal, the power amplifier means including a pair of amplifiers each having a separate output circuit, and a shield winding connected between the output circuits of the amplifiers; a gradient coil having separate first and second portions, each series connected to an opposite end of said amplifier output circuit such that an amplifier-shield winding-amplifier subcircuit is connected between the coil first and second portions; and power switching means for providing a current flow through the series circuit of said amplifier and coil portions to change the coil current responsive to control signals.
Claim 12
Dependent Claim
122 words
A gradient speed-up circuit, for use in a high-speed NMR imaging system, comprising: gradient power amplifier means for controlling a current flowing through an output circuit, responsive to an input signal, the power amplifier means including a pair of amplifiers each having a separate output circuit, and a shield winding connected between the output circuits of the amplifiers; a gradient coil having separate first and second portions, each series connected to an opposite end of said amplifier output circuit such that an amplifier-shield winding-amplifier subcircuit is connected between the coil first and second portions; and power switching means for providing a current flow through the series circuit of said amplifier and coil portions to change the coil current responsive to control signals.
Claim 13
Dependent Claim
28 words
The gradient speed-up circuit of claim 1 in which inductance of the gradient coil and capacitance of the power switching means have values that render the circuit non-resonant.
Claim 14
Dependent Claim
41 words
The gradient speed-up circuit of claim 1 wherein the gradient power amplifier means is responsive to the current passing through the gradient coil and provides high accuracy and stability in its output during both constant current output, and changing current output.
Claim 15
Dependent Claim
42 words
The gradient speed-up circuit of claim 1 wherein the gradient power amplifier means is responsive to a droop in voltage high voltage power supply, and provides high accuracy and stability in its output during both constant current output, and changing current output.
Claim 16
Dependent Claim
31 words
The gradient speed-up circuit of claim 1 wherein the gradient power amplifier means, and the power switching comprise means for generating trapezoidal and triangular pulse current waveforms in the gradient coil.
Claim 17
Dependent Claim
30 words
The gradient speed-up circuit of claim 1 wherein the gradient power amplifier means, and the power switching comprise means for generating sinewave currents by switching off the high-voltage power supply.
Claim 18
Dependent Claim
49 words
The gradient speed-up circuit of claim 1 configured to generate a time-changing current waveform which changes slowly, having an upper set of switches of the full-bridge circuit open and a lower set of switches of the full bridge circuit closed disconnecting the high-voltage power supply from the gradient coil.
Claim 19
Dependent Claim
41 words
The gradient speed-up circuit of claim 1 wherein the gradient power amplifier means includes linear amplifiers whose output voltage is relatively small compared to that of the high voltage power supply so as to provide a high efficiency power conversion circuit.
Claim 20
Dependent Claim
57 words
The gradient speed-up circuit of claim 1 wherein the amplifier means is responsive to the current passing through the gradient coil allowing the gradient power amplifier means to compensate for the reduction in voltage of the high voltage power supply due to the gradient coil losses thereby permitting the use of a low-cost unregulated high voltage supply.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-04-14 | 1995-10-14 | 1996-04-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-04-14 | 1999-10-14 | 2000-04-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-04-14 | 2003-10-14 | 2004-04-14 | $7700.00 | Window Closed / Lapsed |