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US4837513A
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MRI using asymmetric RF nutation pulses and asymmetric synthesis of complex conjugated SE data to reduce TE and T2 decay NMR spin echo responses
Assignee: University of California, San Diego
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Filing: 1988-12-05
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Granted: 1989-06-06
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Expires: 2008-12-05
Abstract
Abstract Reduced T2 decay is achieved through use of at least one asymmetrically truncated RF nutation pulse and an asymmetrically sampled NMR RF response with missing asymmetric data being supplied by complex conjugate synthesis.
Inventors
- 👤 Ching Yao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:57
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/561
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
137 words
In a magnetic resonance imaging system of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having a shaped envelope, the improvement comprising: means for generating and transmitting at least one slice-selective NMR RF pulse with an asymmetric envelope; means for receiving a spin echo NMR RF response, which results at least in part from said RF pulse, during a sampling window which is asymmetrically positioned in the time domain with respect to a maximum envelope peak in the spin echo; and means for asymmetrically synthesizing spin echo response data not actually sampled by use of assumed complex conjugate symmetry so as to supply partly synthesized completed spin echo data representing a theoretical sampling window symmetrically positioned in the time domain about said envelope peak.
Claim 2
Dependent Claim
137 words
In a magnetic resonance imaging system of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having a shaped envelope, the improvement comprising: means for generating and transmitting at least one slice-selective NMR RF pulse with an asymmetric envelope; means for receiving a spin echo NMR RF response, which results at least in part from said RF pulse, during a sampling window which is asymmetrically positioned in the time domain with respect to a maximum envelope peak in the spin echo; and means for asymmetrically synthesizing spin echo response data not actually sampled by use of assumed complex conjugate symmetry so as to supply partly synthesized completed spin echo data representing a theoretical sampling window symmetrically positioned in the time domain about said envelope peak.
Claim 3
Dependent Claim
83 words
An improved magnetic resonance imaging system as in claim 1 wherein said means for generating and transmitting includes: means for generating NMR RF pulses having approximately sinc-shaped envelopes; means for generating and transmitting a first nutation NMR RF pulse having a sinc-shaped envelope truncated asymmetrically; means for generating a magnetic gradient pulse to refocus the NMR spins subsequent to said first nutation pulse; and means for generating and transmitting a subsequent 180° nutation NMR RF pulse having an approximately sinc-shaped envelope truncated symmetrically.
Claim 4
Dependent Claim
45 words
An improved magnetic resonance imaging system as in claim 1 or 2 wherein: said means for generating and transmitting generates said asymmetric envelope by asymmetric truncation of an RF pulse envelope in a direction which causes a reduced T2 decay of the NMR RF response.
Claim 5
Dependent Claim
39 words
An improved magnetic resonance imaging system as in claim 3 wherein: said means for receiving samples said NMR RF response asymmetrically in the time domain in a direction subsequent to a maximum envelope peak of the NMR RF response.
Claim 6
Dependent Claim
104 words
In a magnetic resonance imaging system of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having a shaped envelope and by measuring the resulting NMR RF response during a sampling window, the improvement comprising: means for causing the sampling window to be asymmetrically positioned with respect to a maximum envelope peak in the NMR RF response; and means for asymmetrically synthesizing pseudo NMR RF response data not actually measured so as to supply complete, partly synthesized, NMR RF data representing a theoretical sampling window symmetrically positioned about said maximum envelope peak.
Claim 7
Dependent Claim
104 words
In a magnetic resonance imaging system of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having a shaped envelope and by measuring the resulting NMR RF response during a sampling window, the improvement comprising: means for causing the sampling window to be asymmetrically positioned with respect to a maximum envelope peak in the NMR RF response; and means for asymmetrically synthesizing pseudo NMR RF response data not actually measured so as to supply complete, partly synthesized, NMR RF data representing a theoretical sampling window symmetrically positioned about said maximum envelope peak.
Claim 8
Dependent Claim
28 words
An improved magnetic resonance imaging system as in claim 5 further comprising: means for causing at least one of said RF pulses to have an asymmetrically shaped envelope.
Claim 9
Dependent Claim
39 words
An improved magnetic resonance imaging system as in claim 6 wherein said asymmetric positioning of said sampling window and said asymmetric shaping of the RF pulse envelope are directed to reduce T2 decay of the measured NMR RF response.
Claim 10
Dependent Claim
120 words
In a magnetic resonance imaging method of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having shaped envelope, the improvement comprising: generating and transmitting at least one slice-selective NMR RF pulse with an asymmetric envelope; receiving a spin echo NMR RF response during a sampling window which is asymmetrically positioned in the time domain with respect to a maximum envelope peak in the spin echo; and asymmetrically synthesizing spin echo response data not actually sampled by use of assumed complex conjugate symmetry so as to supply partly synthesized completed spin echo data representing a theoretical sampling window symmetrically positioned in the time domain about said envelope peak.
Claim 11
Dependent Claim
120 words
In a magnetic resonance imaging method of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having shaped envelope, the improvement comprising: generating and transmitting at least one slice-selective NMR RF pulse with an asymmetric envelope; receiving a spin echo NMR RF response during a sampling window which is asymmetrically positioned in the time domain with respect to a maximum envelope peak in the spin echo; and asymmetrically synthesizing spin echo response data not actually sampled by use of assumed complex conjugate symmetry so as to supply partly synthesized completed spin echo data representing a theoretical sampling window symmetrically positioned in the time domain about said envelope peak.
Claim 12
Dependent Claim
56 words
An improved magnetic resonance imaging method as in claim 8 wherein said generating and transmitting step includes: generating NMR RF pulses having sinc-shaped envelopes; generating and transmitting a first nutation NMR RF pulse having a sinc-shaped envelope truncated asymmetrically; and generating and transmitting a subsequent 180° nutation NMR RF pulse having a sinc-shaped envelope truncated symmetrically.
Claim 13
Dependent Claim
44 words
An improved magnetic resonance imaging method as in claim 8 or 9 wherein: said generating and transmitting step generates said asymmetric envelope by asymmetric truncation of an RF pulse envelope in a direction which causes a reduced T2 decay of the NMR RF response.
Claim 14
Dependent Claim
40 words
An improved magnetic resonance imaging method as in claim 10 wherein: said receiving and processing step samples said NMR RF response asymmetrically in the time domain in a direction subsequent to a maximum envelope peak of the NMR RF response.
Claim 15
Dependent Claim
100 words
In a magnetic resonance imaging method of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having a shaped envelope and by measuring the resulting NMR RF response during a sampling window, the improvement comprising: causing the sampling window to be asymmetrically positioned with respect to a maximum envelope peak in the NMR RF response; and asymmetrically synthesizing pseudo NMR RF response data not actually measured so as to supply complete, partly synthesized, NMR RF data representing a theoretical sampling window symmetrically positioned about said maximum envelope peak.
Claim 16
Dependent Claim
100 words
In a magnetic resonance imaging method of the type which elicits NMR RF responses from an imaged object volume by using at least one slice-selective NMR RF pulse having a shaped envelope and by measuring the resulting NMR RF response during a sampling window, the improvement comprising: causing the sampling window to be asymmetrically positioned with respect to a maximum envelope peak in the NMR RF response; and asymmetrically synthesizing pseudo NMR RF response data not actually measured so as to supply complete, partly synthesized, NMR RF data representing a theoretical sampling window symmetrically positioned about said maximum envelope peak.
Claim 17
Dependent Claim
26 words
An improved magnetic resonance imaging method as in claim 12 further comprising: causing at least one of said RF pulses to have an asymmetrically shaped envelope.
Claim 18
Dependent Claim
39 words
An improved magnetic resonance imaging method as in claim 13 wherein said asymmetric positioning of said sampling window and said asymmetric shaping of the RF pulse envelope are directed to reduce T2 decay of the measured NMR RF response.
References Cited (Backward Citations)
US3495162A
Cited
US3496454A
Cited
US4300096A
Cited
US4509015A
Cited
US4573014A
Cited
US4724387A
Cited
US4713616A
Cited
US4724388A
Cited
US4728893A
Cited
US4707661A
Cited
US4737714A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-06-05 | 1992-12-05 | 1993-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-06-05 | 1996-12-05 | 1997-06-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-06-05 | 2000-12-05 | 2001-06-06 | $7700.00 | Window Closed / Lapsed |