Patent EP0222325A2 successfully refreshed from Google Patents.
EP0222325A2
Expired / Lapsed
EP
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Method for reduction of MR image artifacts due to flowing nuclei by gradient moment nulling
Assignee: General Electric Co
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Filing: 1986-11-06
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Granted: —
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Expires: 2006-11-06
Abstract
Abstract A technique has been developed which reduces blood- flow artifacts in multi-echo, multi-slice magnetic resonance (MR) imaging by rephasing spins which have arbitrary velocity as well as static spins. The technique requires tailoring of the gradient structure along at least one of the three axes so as to null out in the preferred embodiment the zeroth and first moments of the gradient distributions.
Inventors
- 👤 Gary Harold Glover
- 👤 Matthew O'donnell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 07:10
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/565; G01R33/56509
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
132 words
A method of compensating for random phase accumulations in magnetic resonance signals acquired from a region of an object having stationary and flowing nuclear spins, said method including the implementation of a plurality of views, each of which includes irradiation of said region by an RF excitation pulse at the Larmor frequency to produce an MR signal, and application of a pulsed magnetic field gradient having adjustable amplitude and duration parameters along at least one dimensional axis of said region, said random phase accumulations being due to fluctuations of flow velocity of said flowing spins from view to view, said method comprising the improvement: modifying at least one of said amplitude and duration parameters so as to make at least one of the higher moments of said magnetic field gradient equal zero.
Claim 2
Independent Claim
132 words
A method of compensating for random phase accumulations in magnetic resonance signals acquired from a region of an object having stationary and flowing nuclear spins, said method including the implementation of a plurality of views, each of which includes irradiation of said region by an RF excitation pulse at the Larmor frequency to produce an MR signal, and application of a pulsed magnetic field gradient having adjustable amplitude and duration parameters along at least one dimensional axis of said region, said random phase accumulations being due to fluctuations of flow velocity of said flowing spins from view to view, said method comprising the improvement: modifying at least one of said amplitude and duration parameters so as to make at least one of the higher moments of said magnetic field gradient equal zero.
Claim 3
Dependent Claim
33 words
The method of Claim 1 wherein irradiation of said region with an RF pulse comprises: irradiating said region with an RF pulse so as to produce a spin-echo signal at a time TE.
Claim 4
Dependent Claim
64 words
The method of Claim 2 wherein said step of modifying comprises satisfying for said flowing nuclear spins the equation: where a = x, y, or z, v is the velocity of nuclear spin flow in the direction of a , TE is the time occurrence of the spin-echo signal, G α is the gradient in the a direction, and -, is the gyromagnetic ratio.
Claim 5
Dependent Claim
40 words
The method of Claim 3 further comprising the step of applying at least one magnetic field gradient along a first dimensional axis of said region to encode spatial information into said spin-echo signal in the direction of said first gradient.
Claim 6
Dependent Claim
32 words
The method of Claim 4,wherein said magnetic field gradient for encoding information is selected to have one of a plurality of directions within said region in the course of implementing said views.
Claim 7
Dependent Claim
38 words
The method of Claim 5 wherein said gradient for encoding information comprises a resultant magnetic field gradient of the vectorial addition of at least two magnetic field gradients, which gradients are perpendicular to one another within said region.
Claim 8
Dependent Claim
47 words
The method of Claim 5 wherein said gradient for encoding information comprises a resultant magnetic field gradient of the vectorial addition of a plurality of magnetic field gradients at least one of which is not coplanar with the remaining ones of said plurality of magnetic field gradients.
Claim 9
Dependent Claim
57 words
The method of Claim 4 further comprising the step of applying, prior to said step of irradiating to produce a spin echo, at least one phase-encoding magnetic field gradient having one of a plurality of amplitude and duration products for phase encoding spatial information into said spin-echo signal in the course of implementing said plurality of views.
Claim 10
Dependent Claim
37 words
The method of Claim 8 wherein said spin-echo signal is sampled in the presence of a substantially linear magnetic field gradient, which gradient is perpendicular to the direction of said phase-encoding magnetic field gradient within said region.
Claim 11
Dependent Claim
82 words
The method of Claim 9 further comprising the step of applying an additional phase-encoding magnetic field gradient selected to be orthogonal to said one phase-encoding magnetic field gradient, said additional phase-encoding gradient having a plurality of amplitude and duration products; and holding the amplitude and duration product of one of said phase-encoding gradients constant, while sequencing through all of the amplitude and duration product of the other phase-encoding gradient, prior to advancing to the amplitude and duration product of said one gradient.
Claim 12
Independent Claim
246 words
A method of compensating for random phase accumulations in magnetic resonance signals acquired from a region of an object having stationary and flowing nuclear spins, said method including the implementation of a plurality of views, each of which includes irradiation of said region by an RF excitation pulse at the Larmor frequency to produce an NMR signal, and application of a pulsed magnetic field gradient having adjustable amplitude and duration parmeters along at least one dimensional axis of said region, said random phase accumulations being due to fluctuations of flow velocity of said flowing spins from view to view, said method comprising the steps: (a) selectively exciting nuclear spins in said region in the presence of a first gradient applied along a first dimensional axis of said region so as to produce a spin-echo signal; (b) applying a phase-encoding magnetic field gradient along a second dimensional axis of said region to encode into said spin-echo signal spatial information in the direction of said second axis; (c) observing said spin echo signal in the presence of a readout magnetic field gradient applied along a third dimensional axis of said region orthogonal to said third axis, to encode spatial information along said third axis; and (d) modifying at least one of said amplitude and duration parameters of at least one of said first, second and third magnetic field gradients so as to make at least one of the higher moments of said one magnetic field gradient equal zero.
Claim 13
Independent Claim
246 words
A method of compensating for random phase accumulations in magnetic resonance signals acquired from a region of an object having stationary and flowing nuclear spins, said method including the implementation of a plurality of views, each of which includes irradiation of said region by an RF excitation pulse at the Larmor frequency to produce an NMR signal, and application of a pulsed magnetic field gradient having adjustable amplitude and duration parmeters along at least one dimensional axis of said region, said random phase accumulations being due to fluctuations of flow velocity of said flowing spins from view to view, said method comprising the steps: (a) selectively exciting nuclear spins in said region in the presence of a first gradient applied along a first dimensional axis of said region so as to produce a spin-echo signal; (b) applying a phase-encoding magnetic field gradient along a second dimensional axis of said region to encode into said spin-echo signal spatial information in the direction of said second axis; (c) observing said spin echo signal in the presence of a readout magnetic field gradient applied along a third dimensional axis of said region orthogonal to said third axis, to encode spatial information along said third axis; and (d) modifying at least one of said amplitude and duration parameters of at least one of said first, second and third magnetic field gradients so as to make at least one of the higher moments of said one magnetic field gradient equal zero.
Claim 14
Dependent Claim
63 words
The method of Claim 11 wherein said step of modifying comprises satisfying for said flowing nuclear spins the equation: where a = x, y, or z, v is the velocity of nuclear spin flow n the direction of α, TE is the time occurrence of the spin-echo signal, G α is the gradient in the a direction, and γ is the gyromagnetic ratio.
References Cited (Backward Citations)
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