Electricity: measuring and testing – Particle precession resonance – Determine fluid flow rate
Reexamination Certificate
2000-11-15
2002-09-17
Arana, Louis (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Determine fluid flow rate
C324S307000
Reexamination Certificate
active
06452390
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the measurement of relative flow between a fluid and a defined volume, such as a pipe, and more particularly, to the measurement of fluid flow and composition by nuclear or electron magnetic resonance.
2. Description of the Prior Art
The idea of studying flow by magnetic resonance dates back to the work of the early pioneers as described, for example, in Mansfield, P; Morris, P. G.; “NMR Imaging in Biomedicine”; Advances in Magnetic Resonance, Supplement 2; 1982; Academic Press, Inc. Orlando 32887; p.235 section 7.3.5. Prior art devices for flow measurement or flow mapping rely on two well-known methods viz. “Time-of-Flight” of saturated or unsaturated spins or “Phase-Encoding” by application of a gradient field along the direction of flow. (Cho, Z. et. al.; “Foundations of Medical Imaging;” John Wiley & Sons, Inc., New York, 1993, p374-386.) Exemplary of the “Time-of-Flight” method is U.S. Pat. No. 4,782,295 to Lew and of the “Phase-Encoding” method is U.S. Pat. No. 5,532,592 to Maneval. Analysis of chemical composition by chemical shift is discussed in “Principles of Magnetic Resonance,” third edition chapter 4, by Slichter, C. P., Springer-Verlag, N.Y. 1989.
SUMMARY OF THE INVENTION
One preferred aspect of the present invention provides a universally applicable simplified method to non-invasively measure the mean value of, or to map the velocity profile of, the various domains of flow based on the dwell time of flowing spins within a defined space containing a constant uniform H
1
Larmor radio frequency excitation field.
Another preferred aspect of the invention provides a method to measure or map the signal received from moving spins within a defined space in the continuous presence of the H
1
Larmor radio frequency excitation field by periodically phase modulating the H
0
strong main magnetic field by a periodic gradient field so as to cause the spins to emit a line or band spectrum, centered at the Larmor frequency, whose sideband amplitudes are known functions of the amplitude of the center-band Larmor frequency signal emitted by the spins, said emitted center-band Larmor frequency signal amplitude being a known function of the dwell time of the spins within a defined space within the H
1
Larmor excitation field.
Another preferred aspect of the invention provides a method to continuously measure the very weak sidebands of the emitted signal from the phase modulated spins in the presence of the very strong H
1
central Larmor field by demodulating and then cross-correlating the received signal with integral multiples of the phase modulating frequency of the periodic gradient field.
In another preferred aspect of the invention, the amplitude of the phase modulating H
0
field is spatially ordered to permit the spatial mapping of the dwell time of the spins within a defined volume within the H
1
excitation Larmor field.
In another preferred aspect of the invention, the pulsed Larmor radio frequency fields and pulsed gradient fields are eliminated, thereby reducing or eliminating eddy currents, transients, and Gibbs truncation artifacts.
Another preferred aspect of the invention provides a method to measure or map the velocity or perfusion vector of the spins from the measurement of, or the map of, the dwell time of the spins within the known geometry of a defined portion of the H
1
Larmor excitation field, said known geometry being defined by a receiver coil preferably wound orthogonal to the H
1
Larmor excitation field coil so as to substantially decouple the noise from, and the signal from, the H
1
Larmor excitation field.
Another preferred aspect of the invention is to provide a measure of, or a map of, the flow velocity or perfusion vector within the known geometry of a defined portion of the H
1
Larmor excitation field constructed from measurements dependent on the dwell time of the spins in a defined portion of the H
1
Larmor frequency excitation field as measured with the known adjustable strength of that H
1
Larmor frequency excitation field, and not significantly dependent on the unknown T
1
spin-lattice, the unknown T
2
spin-spin, the unknown D diffusion, or on other unknown parameters affecting spin magnetization, spin diffusion, or spin coherence. These unknown parameters affect the signal-to-noise of the measurements of this invention, but not significantly the defined end point of these measurements, according to this invention.
A further preferred aspect of this invention is to perform a simultaneous chemical and physical analysis of the flowing material.
A further preferred aspect of this invention is a flow meter for performing one or more of the above methods.
REFERENCES:
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patent: 4455527 (1984-06-01), Singer
patent: 4716367 (1987-12-01), Patz
patent: 4782295 (1988-11-01), Lew
patent: 5408180 (1995-04-01), Mistretta et al.
patent: 5412322 (1995-05-01), Wollin
patent: 5532593 (1996-07-01), Maneval
patent: 5677631 (1997-10-01), Reittinger
patent: 5757187 (1998-05-01), Wollin
patent: 5814988 (1998-09-01), Itskovich et al.
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patent: 6166540 (2000-12-01), Wollin
patent: 496 330 (1992-07-01), None
Mansfield, P; Morris, P.G.: “NMR Imaging in Biomedicine”; Advances in Magnetic Resonance, Supplement 2; 1982, Academic Press, Inc. Orlando 32887; p. 235 section 7.3.5.
Cho, Z. et al.: “Foundations of Medical Imaging”; John Wiley & Sons, Inc., New York, 1993, p 374-386.
Slichter, C.P.: “Principles of Magnetic Resonance,” third edition chapter 2, Springer-Verlag, N.Y. 1989.
Slichter, C.P.: “Principles of Magnetic Resonance,” third edition chapter 4, Springer-Verlag, N.Y. 1989.
Shenberg, Itzhak and Macovski, Albert: “Applications of time-varying gradients in existing magnetic resonance imaging systems”; Med. Phys., vol. 13(2), p 164-169 Mar. 1982, N.Y.
Poularikas, Alexander D.: “The Transforms and Applications Handbook”, CRC-IEEE press, Baca Raton, FL, 1996 pp. 29, 185, 214, 221.
Slichter, C.P.:“Principles of Magnetic Resonance”, third edition, Springer-Verlag, NY 1989 ch. 2.8 p 35-39.
Spitzer, David W.: “Industrial Flow Measurement;” Instrument Society of America, 1990, p 97.
“NMR Measurements of Internal Magnetic Field Gradients Caused by the Presence of an Electric Current in Electrolyte Solutions”, Journal of Magnetic Resonance 40, pp. 595-599, 1980.
Scott, G. C. et al.: “Measurement of Nonuniform Current Density by Magnetic Resonance”, IEEE Transactions on Medical Imaging, vol. 10, No. 3, Sep. 1991, pp. 362-374.
Foley & Lardner
Wollin Ventures, Inc.
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