US4799014A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of setting conditions of high-frequency magnetic field
Assignee: Toshiba Corp
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Filing: 1987-12-11
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Granted: 1989-01-17
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Expires: 2007-12-11
Abstract
Abstract In a method of setting the intensity of a high-frequency magnetic field, in order to adjust and set a field intensity of the high-frequency magnetic field in a magnetic resonance imaging system, an amplitude of an excitation high-frequency magnetic field pulse is sequentially changed; magnetic resonance excitation and reading of a magnetic resonance signal are repeatedly performed; and the amplitude of the high-frequency magnetic field pulse, which corresponds to a maximum or minimum value of the magnetic resonance signal of the signals obtained by a plurality of excitation cycles, is used as a reference to set the intensity of the high-frequency magnetic field. An opposite phase high-frequency magnetic field pulse, having the same amplitude as that of the excitation high-frequency magnetic field pulse, and having a carrier wave which is 180° out of phase with respect to that of the excitation high-frequency magnetic field pulse, is applied to an object after reading of the magnetic resonance signal is completed and before the next magnetic resonance cycle is started.
Inventors
- 👤 Kazuto Nakabayashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 17:15
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/58; G01R33/583
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
169 words
A method of setting the intensity of a high-frequency magnetic field in order to adjust and set a field intensity of the high-frequency magnetic field in a magnetic resonance imaging system, comprising the steps of: (a) sequentially changing the amplitude of an excitation high-frequency magnetic field pulse, (b) repeatedly performing magnetic resonance excitation and reading of a magnetic resonance signal, and (c) utilizing as a reference in setting the intensity of the high-frequency magnetic field the amplitude of the high-frequency magnetic field pulse, which corresponds to one of the maximum and minimum values of the magnetic resonance signal obtained by a plurality of excitation cycles, and (d) applying an opposite phase high-frequency magnetic field pulse, having the same amplitude as that of the excitation high-frequency magnetic field pulse, and having a carrier wave which is 180° out of phase with respect to that of the excitation high-frequency magnetic field pulse, to an object after reading of the magnetic resonance signal is completed and before the next excitation cycle started.
Claim 2
Independent Claim
169 words
A method of setting the intensity of a high-frequency magnetic field in order to adjust and set a field intensity of the high-frequency magnetic field in a magnetic resonance imaging system, comprising the steps of: (a) sequentially changing the amplitude of an excitation high-frequency magnetic field pulse, (b) repeatedly performing magnetic resonance excitation and reading of a magnetic resonance signal, and (c) utilizing as a reference in setting the intensity of the high-frequency magnetic field the amplitude of the high-frequency magnetic field pulse, which corresponds to one of the maximum and minimum values of the magnetic resonance signal obtained by a plurality of excitation cycles, and (d) applying an opposite phase high-frequency magnetic field pulse, having the same amplitude as that of the excitation high-frequency magnetic field pulse, and having a carrier wave which is 180° out of phase with respect to that of the excitation high-frequency magnetic field pulse, to an object after reading of the magnetic resonance signal is completed and before the next excitation cycle started.
Claim 3
Dependent Claim
81 words
A method according to claim 1, further including the step of applying the opposite phase high-frequency magnetic field pulse to the object at a timing symmetrical with that of the excitation high-frequency magnetic field pulse by using each magnetic resonance signal as a center along a time base, and applying a gradient field to the object in a symmetrical manner by using the magnetic resonance signal as the center along the time base after reading of each said magnetic resonance signal.
Claim 4
Dependent Claim
20 words
A method according to claim 1, wherein the magnetic resonance signal is a spin echo signal obtained by magnetic resonance.
Claim 5
Independent Claim
197 words
A method of adjusting and setting a field intensity of a high-frequency magnetic field in a magnetic resonance imaging system, comprising: (1) the first step of applying an excitation high-frequency magnetic field pulse to the object to be examined; (2) the second step of reading a magnetic resonance signal induced into the object; (3) the third step of applying an opposite phase high-frequency magnetic field pulse having the same amplitude as that of the excitation high-frequency magnetic field pulse and having a carrier wave which is 180° out of phase with respect to that of the excitation high-frequency magnetic field pulse; (4) the fourth step of sequentially changing the amplitude of the excitation high-frequency magnetic field pulse and repeating the first through third steps; (5) the fifth step of determining the magnitude of one of the maximum and minimum values of a signal from a plurality of magnetic resonance signals obtained in the fourth step and obtaining an amplitude of the excitation high-frequency magnetic field pulse which corresponds to the determined magnitude; and (6) the sixth step of setting intensity of the high-frequency magnetic field by using, as a reference, the amplitude obtained in the fifth step.
Claim 6
Independent Claim
197 words
A method of adjusting and setting a field intensity of a high-frequency magnetic field in a magnetic resonance imaging system, comprising: (1) the first step of applying an excitation high-frequency magnetic field pulse to the object to be examined; (2) the second step of reading a magnetic resonance signal induced into the object; (3) the third step of applying an opposite phase high-frequency magnetic field pulse having the same amplitude as that of the excitation high-frequency magnetic field pulse and having a carrier wave which is 180° out of phase with respect to that of the excitation high-frequency magnetic field pulse; (4) the fourth step of sequentially changing the amplitude of the excitation high-frequency magnetic field pulse and repeating the first through third steps; (5) the fifth step of determining the magnitude of one of the maximum and minimum values of a signal from a plurality of magnetic resonance signals obtained in the fourth step and obtaining an amplitude of the excitation high-frequency magnetic field pulse which corresponds to the determined magnitude; and (6) the sixth step of setting intensity of the high-frequency magnetic field by using, as a reference, the amplitude obtained in the fifth step.
Claim 7
Dependent Claim
173 words
A method according to claim 4, wherein the first step includes the step of applying a slicing gradient field of a first direction together with the excitation high-frequency magnetic field pulse; a seventh step is provided between the first and second steps to invert and cancel the gradient field of the first direction and apply to the object a gradient field of a second direction which is obtained by inverting a read gradient field; the second step includes the step of acquiring the echo signals, inverting the gradient field of the second direction, and applying a read gradient field to the object; an eighth step is provided between the second and third steps to invert and cancel the gradient field of the second direction and to apply a gradient field, inverted with respect to the gradient field of the first direction, to the object; and the third step includes the step of applying the opposite phase high-frequency magnetic field pulse and a further inverted gradient field of the first direction to the object.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-01-17 | 1992-07-18 | 1993-01-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-01-17 | 1996-07-18 | 1997-01-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-01-17 | 2000-07-18 | 2001-01-17 | $7700.00 | Window Closed / Lapsed |