Patent US973079A successfully refreshed from Google Patents.
Patent EP0256779A2 successfully refreshed from Google Patents.
EP0256779A2
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Rapid NMR imaging system
Assignee: Leland Stanford Junior University
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Filing: 1987-08-05
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Granted: —
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Expires: 2007-08-05
Abstract
Abstract The magnetic resonance activity of a region of a volume is imaged using a time varying gradient whose integral provides a constant velocity spiral in the spatial frequency domain. To provide high fidelity for relatively low values of T₂, high SNR for relatively high values, and a T₂ sensitive image, the spiral is retraced back to the origin. The gradient requirements are minimized using a sequence of interleaved spirals using separate excitations. For further time reduction, only half the spatial frequency domain can be scanned, using inversion excitations to reduce the effects of inhomogeneity.
Inventors
- 👤 Albert Macovski
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 20:02
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/4818; G01R33/4824; G01R33/56; G01R33/561
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
116 words
In a method for providing a magnetic resonance image of a region in a volume the steps of: exciting the region with a radio frequency burst; applying magnetic gradient waveforms to two orthogonal axes where the magnitude of the two gradients is substantially constant and the integral of the gradient waveforms, representing the spatial frequencies of the image, form an array of loops of increasing distance from the origin; applying magnetic gradient waveforms which cause the integral of the gradient waveforms to return to the origin along substantially the same array of loops; receiving magnetic resonant signals while the gradient waveforms are applied; and processing the magnetic resonant signals to produce an image of the region.
Claim 2
Dependent Claim
116 words
In a method for providing a magnetic resonance image of a region in a volume the steps of: exciting the region with a radio frequency burst; applying magnetic gradient waveforms to two orthogonal axes where the magnitude of the two gradients is substantially constant and the integral of the gradient waveforms, representing the spatial frequencies of the image, form an array of loops of increasing distance from the origin; applying magnetic gradient waveforms which cause the integral of the gradient waveforms to return to the origin along substantially the same array of loops; receiving magnetic resonant signals while the gradient waveforms are applied; and processing the magnetic resonant signals to produce an image of the region.
Claim 3
Dependent Claim
29 words
The method as described in claim 1 including the step of repeating the gradient cycles so as to provide additional retracing of the same path through spatial frequency space.
Claim 4
Dependent Claim
50 words
The method as described in claim 1 where the step of applying gradient waveforms includes the step of using waveforms where the radial component and the angular component of the spatial frequencies vary substantially as the square root of time whereby a spiral locus is produced in spatial frequency space.
Claim 5
Dependent Claim
59 words
The method as described in claim 1 where the step of applying gradient waveforms includes the step of applying a sequence of constant amplitude square waveforms to the two orthogonal axes where one gradient is on when the other is off and the waveforms are increasing in duration time whereby a "square" spiral is produced in spatial frequency space.
Claim 6
Dependent Claim
33 words
The method as described in claim 1 where the excitation step includes the step of exciting a plane in the volume whereby the image produced is a cross-sectional image of the excited plane.
Claim 7
Dependent Claim
33 words
The method as described in claim 1 where the excitation step includes the step of exciting the entire volume of interest whereby the image produced is a projection image of the excited volume.
Claim 8
Dependent Claim
123 words
Apparatus for providing a magnetic resoance image of the region in a volume comprising: means for exciting the region with a radio frequency burst; means for applying magnetic gradient waveforms to two orthogonal axes where the magnitude of the two gradients is substantially constant and where the integral of the gradient waveforms, representing the spatial frequencies of the image, form an array of loops of increasing distance from the origin; means for applying magnetic gradient waveforms which cause the integral of the gradient waveforms to return to the origin along substantially the same array of loops; means for receiving magnetic resonant signals while the gradient waveforms are applied; and means for processing the magnetic resonant signals to produce an image of the region.
Claim 9
Dependent Claim
123 words
Apparatus for providing a magnetic resoance image of the region in a volume comprising: means for exciting the region with a radio frequency burst; means for applying magnetic gradient waveforms to two orthogonal axes where the magnitude of the two gradients is substantially constant and where the integral of the gradient waveforms, representing the spatial frequencies of the image, form an array of loops of increasing distance from the origin; means for applying magnetic gradient waveforms which cause the integral of the gradient waveforms to return to the origin along substantially the same array of loops; means for receiving magnetic resonant signals while the gradient waveforms are applied; and means for processing the magnetic resonant signals to produce an image of the region.
Claim 10
Dependent Claim
48 words
Apparatus as described in claim 7 wherein the means for applying gradient waveforms includes means for applying waveforms where the radial spatial frequency component and the angular spatial frequency component vary substantially as the square root of time whereby a spiral locus is produced in spatial frequency space.
Claim 11
Dependent Claim
57 words
Apparatus as described in claim 7 wherein the means for applying gradient waveforms includes means for applying a sequence of constant amplitude square waveforms to the two orthogonal gradient axes where one gradient is on while the other is off and the waveforms are increasing in duration whereby a "square" spiral is produced in spatial frequency space.
Claim 12
Dependent Claim
22 words
Apparatus as described in claim 7 wherein the excited region is a planar section in volume whereby a cross-sectional image is produced.
Claim 13
Dependent Claim
26 words
Apparatus as described in claim 7 wherein the excited region is the entire volume of interest whereby a projection image of the excited volume is produced.
References Cited (Backward Citations)
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