Patent US4947121A successfully refreshed from Google Patents.
US4947121A
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US
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Apparatus and method for enhanced multiple coil nuclear magnetic resonance (NMR) imaging
Assignee: General Electric Co
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Filing: 1989-12-05
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Granted: 1990-08-07
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Expires: 2009-12-05
Abstract
Abstract A nuclear magnetic resonance (NMR) signal acquisition apparatus includes a cylindrical array of overlapping coils. Coupling of currents between coils due to re-radiation of received signals, in particular noise currents, is reduced by presenting a high impedance to each coil, thereby reducing the current circulating in each coil. A PREDAMP circuit is disclosed which utilizes the input impedance of a preamplifier, transformed through a quarter-wavelength transmission line segment, to achieve the high input impedance for the coil. As a result, multiple images, each with a high signal-to-noise ratio (SNR), can be simultaneoulsy obtained. A method is disclosed for combining the multiple images into a composite image with optimum SNR, taking into account the phase shifts between images resulting from the spatial orientation of the coils.
Inventors
- 👤 Cecil E. Hayes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:18
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/32; G01R33/34; G01R33/341; G01R33/3415
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
327 words
A method for combining nuclear magnetic resonance (NMR) signals from M separate NMR receiver coils to produce a composite image represented by a plurality of picture elements (pixels), where M represents a number greater than one which is the number of separate receiver coils, the method comprising the steps of: (a) acquiring a plurality of noise data samples n i from each coil (i) of the M receiver coils during a time period when no NMR signal is present, in which each noise data sample is represented by; n.sub.i =N.sub.i e.sup.jφi (b) producing a set of noise products by computing cross products of the noise data samples for each combination (i,j) of the M receiver coils, and averaging all of the cross products for each said combination, the set of noise products being represented by; <N.sub.i N.sub.j cos(φ.sub.i -φ.sub.j)> where the brackets <>denote an average over the plurality of noise data samples for each combination (i,j); (c) acquiring separate raw imaging data simultaneously from each of the M receiver coils when an NMR signal is present; (d) transforming the raw image data from each of the M receiver coils into separate spatial domain images for each of the M receiver coils, where each spatial domain image includes a plurality of spatial domain image pixels, each spatial domain image pixel being represented by a magnitude S i and a phase θ i for each receiver coil (i); and (e) computing each pixel in the composite image on a pixel by pixel basis by performing the steps of: (f) forming a noise matrix ρij according to the formula; ηij=<N.sub.i N.sub.j cos(φ.sub.i -φ.sub.j)>cos(θ.sub.i -θ.sub.j), for each combination (i,j) of the M receiver coils; (g) inverting the noise matrix to produce ρ -1 ; and (h) computing each pixel in the composite image according to the formula; ##EQU11## where S represents a one dimensional vector formed from the S i magnitudes from each receiver coil (i) of the M receiver coils.
Claim 2
Independent Claim
327 words
A method for combining nuclear magnetic resonance (NMR) signals from M separate NMR receiver coils to produce a composite image represented by a plurality of picture elements (pixels), where M represents a number greater than one which is the number of separate receiver coils, the method comprising the steps of: (a) acquiring a plurality of noise data samples n i from each coil (i) of the M receiver coils during a time period when no NMR signal is present, in which each noise data sample is represented by; n.sub.i =N.sub.i e.sup.jφi (b) producing a set of noise products by computing cross products of the noise data samples for each combination (i,j) of the M receiver coils, and averaging all of the cross products for each said combination, the set of noise products being represented by; <N.sub.i N.sub.j cos(φ.sub.i -φ.sub.j)> where the brackets <>denote an average over the plurality of noise data samples for each combination (i,j); (c) acquiring separate raw imaging data simultaneously from each of the M receiver coils when an NMR signal is present; (d) transforming the raw image data from each of the M receiver coils into separate spatial domain images for each of the M receiver coils, where each spatial domain image includes a plurality of spatial domain image pixels, each spatial domain image pixel being represented by a magnitude S i and a phase θ i for each receiver coil (i); and (e) computing each pixel in the composite image on a pixel by pixel basis by performing the steps of: (f) forming a noise matrix ρij according to the formula; ηij=<N.sub.i N.sub.j cos(φ.sub.i -φ.sub.j)>cos(θ.sub.i -θ.sub.j), for each combination (i,j) of the M receiver coils; (g) inverting the noise matrix to produce ρ -1 ; and (h) computing each pixel in the composite image according to the formula; ##EQU11## where S represents a one dimensional vector formed from the S i magnitudes from each receiver coil (i) of the M receiver coils.
Claim 3
Dependent Claim
92 words
The method according to claim 1 in which: the noise in each receiver coil is assumed to be uncorrelated to the noise in all of the other receiver coils; the set of noise products in step (b) are computed according to the formula; <N.sub.i J.sub.j >, for i=j, and 0 for i≠j; the spatial domain image pixels transformed in step (d) are represented by a magnitude S i only; and in which the noise matrix ρij formed in step (f) thereby reduces to: ρij=<N.sub.i N.sub.j >, for i=j, and ρij=0, for i≠j.
References Cited (Backward Citations)
US4165479A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-08-06 | 1994-02-05 | 1994-08-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-08-06 | 1998-02-05 | 1998-08-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-08-06 | 2002-02-05 | 2002-08-07 | $7700.00 | Window Closed / Lapsed |