Patent US2944697A successfully refreshed from Google Patents.
US4862084A
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Method and system for controlling characteristics of gradient magnetic fields in magnetic resonance imaging apparatus
Assignee: Toshiba Corp
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Filing: 1988-03-14
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Granted: 1989-08-29
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Expires: 2008-03-14
Abstract
Abstract In MRI, in order to provide accurate position data of a subject to an MR signal, the characteristics of the gradient magnetic fields are controlled. The characteristics, i.e., rise time T r of the waveform of a current signal required in generating a gradient magnetic field is described as: T r =(Z l /Z r ) ln (V/V-I out ·Z r )), where Z l is an inductance part of a gradient field generating coil, Z r is a resistance part of a gradient field generating coil, V is a power source voltage of a gradient field generating power source, and I out is a current supplied to the gradient field generating coil. As impedances of the gradient field generating coils are different from one another, the characteristics, for example, rise time periods, of the gradient magnetic fields are controlled by regulating the power source voltage of a gradient magnetic field generating power source. The characteristics of the gradient magnetic fields are also controlled by making trapezoidal waves.
Inventors
- 👤 Michio Mitomi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 06:54
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/385
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
102 words
A method for controlling waveforms of coil currents supplied to gradient magnetic field generating coil systems from magnetic field generating power sources, the method comprising the sequence of steps of: supplying the coil currents to the gradient magnetic field generating coil systems while detecting the waveforms of the coil currents; controlling the waveforms of the coil currents in response to the detected waveforms of the supplied coil currents to achieve a predetermined agreement among the waveforms of the coil currents; and supplying the coil currents having the controlled waveforms to the gradient magnetic field generating coil systems to generate gradient magnetic fields.
Claim 2
Independent Claim
102 words
A method for controlling waveforms of coil currents supplied to gradient magnetic field generating coil systems from magnetic field generating power sources, the method comprising the sequence of steps of: supplying the coil currents to the gradient magnetic field generating coil systems while detecting the waveforms of the coil currents; controlling the waveforms of the coil currents in response to the detected waveforms of the supplied coil currents to achieve a predetermined agreement among the waveforms of the coil currents; and supplying the coil currents having the controlled waveforms to the gradient magnetic field generating coil systems to generate gradient magnetic fields.
Claim 3
Dependent Claim
31 words
A method according to claim 1, wherein the waveforms of the coil currents supplied to the gradient magnetic field generating coil systems are controlled in accordance with a waveform rise time.
Claim 4
Dependent Claim
27 words
A method according to claim 2, wherein the rise time is set to be the longest rise time period among the detected waveforms of the coil currents.
Claim 5
Dependent Claim
25 words
A method according to claim 1, wherein the controlling step includes a step of regulating power source voltages of the magnetic field generating power sources.
Claim 6
Dependent Claim
31 words
A method according to claim 4, wherein the waveforms of the coil currents supplied to the gradient magnetic field generating coil systems are controlled in accordance with a waveform rise time.
Claim 7
Dependent Claim
27 words
A method according to claim 5, wherein the rise time is set to be the longest rise time period among the detected waveforms of the coil currents.
Claim 8
Dependent Claim
27 words
A method according to claim 1, wherein the controlling step includes a step of generating trapezoidal waves in accordance with the waveforms of the detected coil currents.
Claim 9
Dependent Claim
31 words
A method according to claim 7, wherein the waveforms of the coil currents supplied to the gradient magnetic field generating coil systems are controlled in accordance with a waveform rise time.
Claim 10
Dependent Claim
27 words
A method according to claim 8, wherein the rise time is set to be the longest rise time period among the detected waveforms of the coil currents.
Claim 11
Independent Claim
98 words
A system for controlling waveforms of coil currents supplied to gradient magnetic field generating coil systems from magnetic field generating power sources, the system comprising: means for supplying the coil currents to the gradient magnetic field generating coil systems; and means for controlling the waveforms of the coil currents by detecting the waveforms of the supplied coil currents to achieve a predetermined agreement among the waveforms of the coil currents, and operating the supplying means to supply the coil currents having the agreed waveforms to the gradient magnetic field generating coil systems to generate the gradient magnetic fields.
Claim 12
Independent Claim
98 words
A system for controlling waveforms of coil currents supplied to gradient magnetic field generating coil systems from magnetic field generating power sources, the system comprising: means for supplying the coil currents to the gradient magnetic field generating coil systems; and means for controlling the waveforms of the coil currents by detecting the waveforms of the supplied coil currents to achieve a predetermined agreement among the waveforms of the coil currents, and operating the supplying means to supply the coil currents having the agreed waveforms to the gradient magnetic field generating coil systems to generate the gradient magnetic fields.
Claim 13
Dependent Claim
31 words
A system according to claim 10, wherein the waveforms of the coil currents supplied to the gradient magnetic field generating coil systems are controlled in accordance with a waveform rise time.
Claim 14
Dependent Claim
32 words
A system according to claim 11, wherein the rise time is set to be the longest rise time period among the detected waveforms of the coil currents detected by the controlling means.
Claim 15
Dependent Claim
24 words
A system according to claim 10, wherein the controlling means includes means for regulating power source voltages of the magnetic field generating power sources.
Claim 16
Dependent Claim
31 words
A system according to claim 13, wherein the waveforms of the coil currents supplied to the gradient magnetic field generating coil systems are controlled in accordance with a waveform rise time.
Claim 17
Dependent Claim
31 words
A system according to claim 14, wherein the rise time is set to be the longest rise time period among the waveforms of the coil currents detected by the controlling means.
Claim 18
Dependent Claim
27 words
A system according to claim 10, wherein the controlling means includes means for generating the trapezoidal waves in accordance with the waveforms of the detected coil currents.
Claim 19
Dependent Claim
31 words
A system according to claim 16, wherein the waveforms of the coil currents supplied to the gradient magnetic field generating coil systems are controlled in accordance with a waveform rise time.
Claim 20
Dependent Claim
31 words
A system according to claim 17, wherein the rise time is set to be the longest rise time period among the waveforms of the coil currents detected by the controlling means.
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) | 1992-08-28 | 1993-02-27 | 1993-08-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-28 | 1997-02-27 | 1997-08-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-28 | 2001-02-27 | 2001-08-29 | $7700.00 | Window Closed / Lapsed |