US5270657A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Split gradient amplifier for an MRI system
Assignee: General Electric Co
•
Filing: 1992-10-22
•
Granted: 1993-12-14
•
Expires: 2012-10-22
Abstract
Abstract A gradient amplifier for use in magnetic resonance imaging equipment employs a low voltage DC power supply connected in series between a pair of higher voltage DC power supplies, the latter supplies serving to provide increased power for rapid gradient switching and the former supply providing correction current to produce the desired voltage output. The high voltage DC power supplies preferably comprise multiple DC units which can be combined to provide finer steps of control prior to correction by the lower voltage supply. The low voltage DC power supply preferably comprise one or more linear amplifiers connected in series, or one or more switchmode amplifiers connected in series. The DC power supplies are controlled in an open loop manner from a gradient signal that designates the desired current for the gradient coil and the amplifiers are operated in a closed loop responding to to a feedback signal from the gradient coil.
Inventors
- 👤 William F. Wirth
- 👤 Thomas G. McFarland
- 👤 Robert M. Vavrek
- 👤 Peter B. Roemer
- 👤 Otward M. Mueller
- 👤 John N. Park
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 11:04
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/385; G01R33/3852
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
196 words
An amplifier for a gradient oil of a magnetic resonance imaging system, the amplifier receiving a gradient signal and producing voltage to generate a gradient current in a gradient coil to produce a desired magnetic gradient field, the amplifier comprising: a DC power supply having an input for receiving the gradient signal and having an output connected to the gradient coil for impressing a first voltage component across the gradient coil, the first voltage component being selectable from a discontinuous range of output voltages and approximating the voltage needed to produce the gradient current; a feedback sensor connected to the gradient coil for producing a feedback signal indicative of a magnetic gradient field produced by the gradient coil; and an amplifier device having an output connected to the gradient coil for impressing a second voltage component across the gradient coil, the second voltage component being within a continuous range of output voltages, and having an input receiving the feedback signal and the gradient signal to adjust the second voltage component so that the sum of the first and second voltage components generates the gradient current in the gradient coil to produce the desired magnetic gradient field.
Claim 2
Dependent Claim
196 words
An amplifier for a gradient oil of a magnetic resonance imaging system, the amplifier receiving a gradient signal and producing voltage to generate a gradient current in a gradient coil to produce a desired magnetic gradient field, the amplifier comprising: a DC power supply having an input for receiving the gradient signal and having an output connected to the gradient coil for impressing a first voltage component across the gradient coil, the first voltage component being selectable from a discontinuous range of output voltages and approximating the voltage needed to produce the gradient current; a feedback sensor connected to the gradient coil for producing a feedback signal indicative of a magnetic gradient field produced by the gradient coil; and an amplifier device having an output connected to the gradient coil for impressing a second voltage component across the gradient coil, the second voltage component being within a continuous range of output voltages, and having an input receiving the feedback signal and the gradient signal to adjust the second voltage component so that the sum of the first and second voltage components generates the gradient current in the gradient coil to produce the desired magnetic gradient field.
Claim 3
Dependent Claim
78 words
The amplifier as recited in claim 1 wherein the DC power supply has more than one DC source with each DC source being switchable to produce incremental voltage or zero voltage, such DC sources being connected so that the sum of the incremental voltages defines the discontinuous range of output voltages and so that the first voltage component is the sum of only the incremental voltages from those DC sources that are switched to produce an incremental voltage.
Claim 4
Dependent Claim
27 words
The amplifier as recited in claim 2 wherein the incremental voltages for each DC source differ in value between each DC source according to a binary relationship.
Claim 5
Dependent Claim
37 words
The amplifier as recited in claim 1 wherein the feedback sensor is a resistor connected in series with the gradient coil to generate a voltage proportional to the gradient current and hence to the gradient magnetic field.
Claim 6
Dependent Claim
37 words
The amplifier as recited in claim 1 wherein the DC power supply is a precharged capacitor which may be connected to or disconnected from the gradient coil to generate either a first voltage component or zero voltage.
Claim 7
Dependent Claim
76 words
The amplifier as recited in claim 5 comprising: a source of a reference signal that indicates a desired peak capacitor voltage; and an error voltage generator having a first input for receiving the reference voltage, a second input for receiving a signal representing a voltage on the capacitor, and an output coupled to the amplifier device for altering the second voltage component to move a peak voltage across the capacitor toward the desired peak capacitor voltage.
Claim 8
Dependent Claim
37 words
The amplifier as recited in claim 6 wherein the error voltage generator is gated to produce the third voltage component only during changes in the gradient current caused by changes in the first or second voltage components.
Claim 9
Dependent Claim
221 words
In a magnetic resonance imaging system, an apparatus which receives a gradient current signal and produces a corresponding gradient current in a gradient coil to generate a desired magnetic gradient field, the apparatus comprising: a differentiator for differentiating the gradient current signal to produce a driving voltage signal; a DC power supply having an output connected to the gradient coil for impressing, across the gradient coil, a first voltage component that is selectable from a discontinuous range of output voltages; a digitizer for receiving the driving voltage signal and connected to the DC power supply to produce a digital switching signal to select the first voltage component from the discontinuous range of output voltages to approximate the voltage needed to generate the gradient current; a feedback sensor connected to the gradient coil for producing a feedback signal indicative of the gradient current; and an amplifier having an output connected to the gradient coil for impressing a second voltage component across the gradient coil, the second voltage component being within a continuous range of output voltages, and the amplifier receiving and responsive to the feedback signal and the gradient signal by adjusting the second voltage component so that the sum of the first and second voltage components generates the gradient current in the gradient coil to produce the desired magnetic gradient field.
Claim 10
Dependent Claim
221 words
In a magnetic resonance imaging system, an apparatus which receives a gradient current signal and produces a corresponding gradient current in a gradient coil to generate a desired magnetic gradient field, the apparatus comprising: a differentiator for differentiating the gradient current signal to produce a driving voltage signal; a DC power supply having an output connected to the gradient coil for impressing, across the gradient coil, a first voltage component that is selectable from a discontinuous range of output voltages; a digitizer for receiving the driving voltage signal and connected to the DC power supply to produce a digital switching signal to select the first voltage component from the discontinuous range of output voltages to approximate the voltage needed to generate the gradient current; a feedback sensor connected to the gradient coil for producing a feedback signal indicative of the gradient current; and an amplifier having an output connected to the gradient coil for impressing a second voltage component across the gradient coil, the second voltage component being within a continuous range of output voltages, and the amplifier receiving and responsive to the feedback signal and the gradient signal by adjusting the second voltage component so that the sum of the first and second voltage components generates the gradient current in the gradient coil to produce the desired magnetic gradient field.
Claim 11
Independent Claim
212 words
An apparatus for receiving a gradient signal and producing voltage to generate a current in a gradient coil of a magnetic resonance imaging system, the apparatus comprising: a controller which produces first and second control signals from the gradient signal; a first DC power supply having an input connected to said controller for receiving the first control signal and having first and second output terminals across which is produced a first voltage component having a magnitude adjustable in response to the first control signal, and the first output terminal being coupled to the gradient coil; a second DC power supply having an input connected to said controller for receiving the first control signal and having third and fourth output terminals across which is produced a second voltage component having a magnitude adjustable in response to the first control signal, and the fourth output terminal being coupled to the gradient coil; and an amplifier assembly responsive to the second control signal by producing a third voltage component at an output that is connected between the second and third terminals of said first and second DC power supplies, so that the sum of the first, second and third voltage components generates the current in the gradient coil to produce the desired magnetic gradient field.
Claim 12
Independent Claim
212 words
An apparatus for receiving a gradient signal and producing voltage to generate a current in a gradient coil of a magnetic resonance imaging system, the apparatus comprising: a controller which produces first and second control signals from the gradient signal; a first DC power supply having an input connected to said controller for receiving the first control signal and having first and second output terminals across which is produced a first voltage component having a magnitude adjustable in response to the first control signal, and the first output terminal being coupled to the gradient coil; a second DC power supply having an input connected to said controller for receiving the first control signal and having third and fourth output terminals across which is produced a second voltage component having a magnitude adjustable in response to the first control signal, and the fourth output terminal being coupled to the gradient coil; and an amplifier assembly responsive to the second control signal by producing a third voltage component at an output that is connected between the second and third terminals of said first and second DC power supplies, so that the sum of the first, second and third voltage components generates the current in the gradient coil to produce the desired magnetic gradient field.
Claim 13
Dependent Claim
87 words
The apparatus as recited in claim 9 wherein at least one of said first and second DC power supplies has more than one DC source, each such DC source being switchable to produce an incremental voltage or zero voltage, the DC sources connected so that the sum of the incremental voltages define a range of output voltages and so that the corresponding first or second voltage component is the sum of only the incremental voltages from those DC sources that are switched to produce an incremental voltage.
Claim 14
Dependent Claim
28 words
The apparatus as recited in claim 10 wherein the incremental voltages for each DC source differ in value between each DC source in according to a binary relationship.
Claim 15
Dependent Claim
88 words
The apparatus as recited in claim 9 wherein each one of said first and second DC power supplies comprises: a source of a DC voltage; four diodes connected as a full wave rectifier bridge having positive and negative nodes connected to said source of a DC voltage and having another pair of nodes which are connected to the output terminals of said DC power supply; and four switch elements each being connected across one of said diodes and being rendered conductive in response to the second control signal.
Claim 16
Dependent Claim
16 words
The apparatus as recited in claim 9 wherein said amplifier assembly comprises a single linear amplifier.
Claim 17
Dependent Claim
36 words
The apparatus as recited in claim 9 wherein said amplifier assembly comprises a pair of linear amplifiers with outputs connected in series between the second and third terminals of said first and second DC power supplies.
Claim 18
Dependent Claim
61 words
The apparatus as recited in claim 14 wherein said amplifier assembly further comprises a current sensing resistor coupling the outputs of said pair of linear amplifiers, one end of said resistor being connected to ground and another end of said resistor being coupled to said controller to provide a signal indicative of a magnitude of current flowing through the gradient coil.
Claim 19
Dependent Claim
27 words
The apparatus as recited in claim 9 wherein said amplifier assembly comprises a single linear switchmode amplifier having a DC source that produces the third voltage component.
Claim 20
Dependent Claim
23 words
The apparatus as recited in claim 9 wherein the third voltage component is less than each of the first and second voltage components.
Claim 21
Dependent Claim
36 words
The apparatus as recited in claim 9 wherein said amplifier assembly includes a pair of switchmode amplifiers with outputs connected in series between the second and third terminals of said first and second DC power supplies.
Claim 22
Dependent Claim
93 words
The apparatus as recited in claim 18 wherein each of said switchmode amplifiers comprises: a source of DC voltage which is less than each of the first and second voltage components; a set of four diodes connected as a full wave rectifier bridge having positive and negative nodes connected to said DC voltage source and having another pair of nodes which form the output said switchmode amplifier; and four switch elements each being connected across one of the diodes in said set and being rendered conductive in response to the second control signal.
Claim 23
Dependent Claim
36 words
The apparatus as recited in claim 9 wherein said first and second DC power supplies select the first and second voltage components, respectively, from a group of voltage levels in response to the first control signal.
Claim 24
Independent Claim
232 words
An apparatus for receiving a gradient signal and producing voltage to generate a current in a gradient coil of a magnetic resonance imaging system, the apparatus comprising: a first DC power supply having an input for receiving a first control signal and having first and second output terminals across which is produced a first voltage component selectable from a group of voltage levels in response to the first control signal, and the first output terminal being coupled to the gradient coil; a second DC power supply having an input for receiving the first control signal and having third and fourth output terminals across which is produced a second voltage component selectable from a group of voltage levels in response to the first control signal, and the fourth output terminal being coupled to the gradient coil; a switchmode amplifier assembly responsive to a second control signal by producing a third voltage component at an output that is connected in series between the second and third output terminals of said first and second DC power supplies, so that the sum of the first, second and third voltage components generates the current in the gradient coil to produce the desired magnetic gradient field; and a controller which produces the first and second control signals from the gradient signal, and being connected to said switchmode amplifier assembly and to said first and second DC power supplies.
Claim 25
Independent Claim
232 words
An apparatus for receiving a gradient signal and producing voltage to generate a current in a gradient coil of a magnetic resonance imaging system, the apparatus comprising: a first DC power supply having an input for receiving a first control signal and having first and second output terminals across which is produced a first voltage component selectable from a group of voltage levels in response to the first control signal, and the first output terminal being coupled to the gradient coil; a second DC power supply having an input for receiving the first control signal and having third and fourth output terminals across which is produced a second voltage component selectable from a group of voltage levels in response to the first control signal, and the fourth output terminal being coupled to the gradient coil; a switchmode amplifier assembly responsive to a second control signal by producing a third voltage component at an output that is connected in series between the second and third output terminals of said first and second DC power supplies, so that the sum of the first, second and third voltage components generates the current in the gradient coil to produce the desired magnetic gradient field; and a controller which produces the first and second control signals from the gradient signal, and being connected to said switchmode amplifier assembly and to said first and second DC power supplies.
Claim 26
Dependent Claim
94 words
The apparatus as recited in claim 21 wherein said switchmode amplifier assembly comprises: a first source of DC voltage which is less than each of the first and second voltage components; a first set of four diodes connected as a full wave rectifier bridge having positive and negative nodes connected to said first source of DC voltage and having first and second output nodes; and a first quartet of switches with each switch being connected across a different diode in said first set, and being rendered conductive in response to the second control signal.
Claim 27
Dependent Claim
104 words
The apparatus as recited in claim 22 wherein said switchmode amplifier assembly further comprises: a second source of DC voltage which is less than each of the first and second voltage components; a second set of four diodes connected as a full wave rectifier bridge having positive and negative nodes connected to said second source of DC voltage, and having third and fourth output nodes with the third node being coupled to the second node; and a second quartet of switches with each being connected across a different diode in said second set, and being rendered conductive in response to the second control signal.
Claim 28
Independent Claim
361 words
An apparatus for receiving a gradient signal and producing a voltage to generate a current in a gradient coil of a magnetic resonance imaging system, the apparatus, said apparatus comprising: a controller which produces first and second control signals and an analog signal from the gradient signal; a first DC power supply having an input connected to said controller for receiving the first control signal and having first and second output terminals across which is produced a first voltage component selectable from a plurality of voltage levels in response to the first control signal, and the first output terminal being coupled to the gradient coil; a second DC power supply having an input connected to said controller for receiving the second control signal and having third and fourth output terminals across which is produced a second voltage component selectable from a group of voltage levels in response to the first control signal, and the third output terminal being coupled to the second output terminal of said first DC power supply; a third DC power supply having an input connected to said controller for receiving the first control signal and having fifth and sixth output terminals across which is produced a third voltage component selectable from a plurality of voltage levels in response to the first control signal, and the fifth output terminal being coupled to the gradient coil; a fourth DC power supply having an input connected to said controller for receiving the second control signal and having seventh and eighth output terminals across which is produced a fourth voltage component selectable from a group of voltage levels in response to the second control signal, and the seventh output terminal being coupled to the sixth output terminal of said third DC power supply; and a pair of linear amplifiers which respond to the analog signal by producing a fifth voltage component across at a pair of terminals connected between the fourth and eighth output terminals of said second and fourth DC power supplies, so that the sum of the first, second, third, fourth and fifth voltage components generates the current in the gradient coil to produce the desired magnetic gradient field.
Claim 29
Independent Claim
361 words
An apparatus for receiving a gradient signal and producing a voltage to generate a current in a gradient coil of a magnetic resonance imaging system, the apparatus, said apparatus comprising: a controller which produces first and second control signals and an analog signal from the gradient signal; a first DC power supply having an input connected to said controller for receiving the first control signal and having first and second output terminals across which is produced a first voltage component selectable from a plurality of voltage levels in response to the first control signal, and the first output terminal being coupled to the gradient coil; a second DC power supply having an input connected to said controller for receiving the second control signal and having third and fourth output terminals across which is produced a second voltage component selectable from a group of voltage levels in response to the first control signal, and the third output terminal being coupled to the second output terminal of said first DC power supply; a third DC power supply having an input connected to said controller for receiving the first control signal and having fifth and sixth output terminals across which is produced a third voltage component selectable from a plurality of voltage levels in response to the first control signal, and the fifth output terminal being coupled to the gradient coil; a fourth DC power supply having an input connected to said controller for receiving the second control signal and having seventh and eighth output terminals across which is produced a fourth voltage component selectable from a group of voltage levels in response to the second control signal, and the seventh output terminal being coupled to the sixth output terminal of said third DC power supply; and a pair of linear amplifiers which respond to the analog signal by producing a fifth voltage component across at a pair of terminals connected between the fourth and eighth output terminals of said second and fourth DC power supplies, so that the sum of the first, second, third, fourth and fifth voltage components generates the current in the gradient coil to produce the desired magnetic gradient field.
Claim 30
Dependent Claim
99 words
The apparatus as recited in claim 24 wherein each one of said first, second, third and fourth DC power supplies comprises: a source of a DC voltage; four diodes connected as a full wave rectifier bridge having positive and negative nodes connected to said source of a DC voltage and having another pair of nodes which are connected to the output terminals of one of said first, second, third and fourth DC power supplies; and four switch elements each being connected across one of said diodes and being rendered conductive in response to a control signal from said controller.
References Cited (Backward Citations)
US4437053A
Cited
US4668904A
Cited
US4916395A
Cited
US5017871A
Cited
US5066914A
Cited
US5045990A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-12-13 | 1997-06-14 | 1997-12-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-12-13 | 2001-06-14 | 2001-12-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-12-13 | 2005-06-14 | 2005-12-14 | $7700.00 | Window Closed / Lapsed |