US5655531A
Expired / Lapsed
US
⏱️ 0.0 years remaining
MRI method and apparatus for selective image suppression of material based on T1 and T2 relation times
Assignee: Leland Stanford Junior University
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Filing: 1995-05-15
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Granted: 1997-08-12
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Expires: 2015-05-15
Abstract
Abstract The selective imaging of an object having two materials with different relaxation times (T1 or T2) is provided by using a driven equilibrium sequence (T2 weighted preparation sequence) followed by an inversion recovery sequence. In the driven equilibrium sequence the object is placed in a static magnetic field along a longitudinal axis, an excitation pulse is applied to tip nuclei spins into a transverse plane, and at least one refocusing pulse is applied to produce a spin echo having a magnetization component as a function of relaxation time. At least one pulse is then applied to the object to drive the spin echo to an inverted position along the longitudinal axis. A readout excitation is then applied at a later time when the longitudinal magnetization of one material is substantially reduced. In one embodiment, an inversion pulse is applied prior to the T2 weighted preparation sequence.
Inventors
- 👤 Dwight G. Nishimura
- 👤 Jean H. Brittain
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 00:25
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/50
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
130 words
A method of selectively suppressing magnetic resonance signals in an object having at least two materials therein with different relaxation times, said method comprising the steps of a) positioning said object in a magnetic field along a longitudinal axis, b) applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, c) applying at least one refocusing pulse to said object to produce a spin echo at a time TE, said spin echo including a magnetization component as a function of relaxation time, d) applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, and e) applying a readout excitation at a time TI when the longitudinal magnetization of one material is substantially reduced.
Claim 2
Independent Claim
130 words
A method of selectively suppressing magnetic resonance signals in an object having at least two materials therein with different relaxation times, said method comprising the steps of a) positioning said object in a magnetic field along a longitudinal axis, b) applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, c) applying at least one refocusing pulse to said object to produce a spin echo at a time TE, said spin echo including a magnetization component as a function of relaxation time, d) applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, and e) applying a readout excitation at a time TI when the longitudinal magnetization of one material is substantially reduced.
Claim 3
Dependent Claim
47 words
The method as defined by claim 1 wherein step d) includes the steps of applying an excitation pulse to said object to drive said spin echo to an uninverted position along said longitudinal axis, and applying another excitation pulse to said object to invert said magnetization component.
Claim 4
Dependent Claim
55 words
The method as defined by claim 2 wherein said first excitation pulse is a 90° pulse, in step c) said at least one refocusing pulse includes a 180° pulse, in step d) said excitation pulse is a -90° pulse, said another excitation pulse is a 180° pulse, and said readout excitation is a 90° pulse.
Claim 5
Dependent Claim
18 words
The method as defined by claim 1 wherein step d) includes applying a +90° pulse to said object.
Claim 6
Dependent Claim
17 words
The method as defined by claim 1 wherein said different relaxation times are spin-spin (T2) relaxation times.
Claim 7
Dependent Claim
17 words
The method as defined by claim 1 wherein said different relaxation times are spin-lattice (T1) relaxation times.
Claim 8
Independent Claim
140 words
A method of selectively suppressing magnetic resonance signals in an object having at least two materials therein with different relaxation times, said method comprising the steps of a) positioning said object in a magnetic field along a longitudinal axis, b) applying an inversion pulse to invert nuclei spins, c) applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, d) applying at least one refocusing pulse to said object to produce a spin echo at a time TE, said spin echo including a magnetization component as a function of relaxation time, e) applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, and f) applying a readout excitation at a readout time TI when the longitudinal magnetization of one material is substantially reduced.
Claim 9
Independent Claim
140 words
A method of selectively suppressing magnetic resonance signals in an object having at least two materials therein with different relaxation times, said method comprising the steps of a) positioning said object in a magnetic field along a longitudinal axis, b) applying an inversion pulse to invert nuclei spins, c) applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, d) applying at least one refocusing pulse to said object to produce a spin echo at a time TE, said spin echo including a magnetization component as a function of relaxation time, e) applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, and f) applying a readout excitation at a readout time TI when the longitudinal magnetization of one material is substantially reduced.
Claim 10
Dependent Claim
130 words
Apparatus for use in magnetic resonance imaging of an object having at least two materials therein with different relaxation times, said apparatus comprising a) means for applying a static magnetic field through said object along a longitudinal axis, b) means for applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, c) means for applying at least one refocusing pulse to said object to produce a spin echo at a time TE, d) means for applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, e) means for applying a readout excitation at a readout time when longitudinal magnetization of one material is substantially reduced, and f) means for detecting a readout signal.
Claim 11
Dependent Claim
130 words
Apparatus for use in magnetic resonance imaging of an object having at least two materials therein with different relaxation times, said apparatus comprising a) means for applying a static magnetic field through said object along a longitudinal axis, b) means for applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, c) means for applying at least one refocusing pulse to said object to produce a spin echo at a time TE, d) means for applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, e) means for applying a readout excitation at a readout time when longitudinal magnetization of one material is substantially reduced, and f) means for detecting a readout signal.
Claim 12
Dependent Claim
43 words
Apparatus as defined by claim 8 wherein said d) means applies an excitation pulse to said object to drive said spin echo to an uninverted orientation along said longitudinal axis, and applies another excitation pulse to said object to invert said magnetization component.
Claim 13
Dependent Claim
56 words
Apparatus as defined by claim 9 wherein said first excitation pulse is a 90° pulse, in said c) element said at least one refocusing pulse includes a 180° pulse, in said d) element said excitation pulse is a -90° pulse, said another excitation pulse is a 180° pulse, and said readout excitation is a 90° pulse.
Claim 14
Dependent Claim
17 words
Apparatus as defined by claim 8 wherein said d) means applies a 90° pulse to said object.
Claim 15
Dependent Claim
143 words
Apparatus for use in magnetic resonance imaging of an object having at least two materials therein with different relaxation times, said apparatus comprising means for applying a static magnetic field through said object along a longitudinal axis, means for applying an inversion pulse to invert nuclei spins, means for applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, means for applying at least one refocusing pulse to said object to produce a spin echo at a time TE, said spin echo including a magnetization component as a function of relaxation time, means for applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, and means for applying a readout excitation at a readout time TI when the longitudinal magnetization of one material is substantially reduced.
Claim 16
Dependent Claim
143 words
Apparatus for use in magnetic resonance imaging of an object having at least two materials therein with different relaxation times, said apparatus comprising means for applying a static magnetic field through said object along a longitudinal axis, means for applying an inversion pulse to invert nuclei spins, means for applying a first excitation pulse to said object to tip nuclei spins into a transverse plane, means for applying at least one refocusing pulse to said object to produce a spin echo at a time TE, said spin echo including a magnetization component as a function of relaxation time, means for applying at least one pulse to said object to drive said spin echo to an inverted position along said longitudinal axis, and means for applying a readout excitation at a readout time TI when the longitudinal magnetization of one material is substantially reduced.
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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) | 2000-08-11 | 2001-02-10 | 2001-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-08-11 | 2005-02-10 | 2005-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-08-11 | 2009-02-10 | 2009-08-12 | $7700.00 | Window Closed / Lapsed |