Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1991-02-14
1992-10-06
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
G01R 3320
Patent
active
051535157
ABSTRACT:
Methods of constructing pulse sequences to selectively excite frequency bands in NMR imaging, spectroscopic and optical systems are disclosed. In preferred embodiments, selective .pi./2, .pi., and refocusing hard and soft pulses are constructed for perturbing the spins of the system. In NMR imaging, for example, the desired magnetization is written as an (N+1)th order Fourier series in .omega.t, where .omega. is the off-resonance frequency. In addition, if all pulses have the same phase, then the z magnetization is known to be symmetric in frequency, and the resulting hard pulse sequence can be written as an Nth order Fourier cosine series. Given this Fourier series representing the desired z magnetization, an inversion may be used to determine the hard pulse sequence of N pulses which will actually yield the desired response. In particular, if one starts with a specification of a desired z magnetization not as a Fourier series in .omega.t, but rather as having certain desired values over several frequency ranges, the techniques of finite impulse response filters may be applied to yield the desired Fourier series representing the z and xy magnetizations. The optimal hard pulse sequence which yields that Fourier series may then be mathematically determined and applied to the system to yield the desired response. In accordance with another feature of the invention, the synthesized hard pulse sequence may be used to generate a soft pulse which has a frequency response over a broad range which is the same as that of the synthesized hard pulse sequence. The methods of the invention thus allow for the generation of optimal pulse sequences without the use of linear Fourier transform approximations to intrinsically nonlinear systems.
REFERENCES:
patent: 3810001 (1974-05-01), Ernst
patent: 4173722 (1979-11-01), Detering
patent: 4630188 (1986-12-01), Daggett
patent: 4695798 (1987-09-01), Brandes
patent: 4701708 (1987-10-01), Hardy et al.
patent: 4766380 (1988-08-01), Den Boef et al.
patent: 4780673 (1988-10-01), Hill
patent: 4789831 (1988-12-01), Mayo, Jr.
patent: 4876507 (1989-10-01), Van Vaals
I. V. Aleksandrov, The Theory of Nuclear Magnetic Resonance, pp. 169-181, Academic Press, NY, 1966 (Textbook).
S. M. Eleff et al., "The Synthesis of Pulse Sequences Yielding Arbitrary Magnetization Vectors", Journal of Magnetic Resonance in Medicine, vol. 12, pp. 74-80 (1989).
P. J. Hore, "Solvent Suppression in Fourier Transform Nuclear Magnetic Resonance", Journal of Magnetic Resonance, vol. 55, pp. 283-300 (1983).
L. D. Landau and E. M. Lifschitz, Quantum Mechanics: Non Relativistic Theory, pp. 188-196, Pergamon Press, London, 1965 (Textbook).
A. V. Oppenheim & R. W. Schaefer, Digital Signal Processing, pp. 237-267, Prentice Hall, New Jersey, 1975 (Textbook).
M. Shinnar and J. S. Leigh, "Frequency Response of Soft Pulses", Journal of Magnetic Resonance, vol. 75, pp. 502-505 (1987).
M. Shinnar and J. S. Leigh, "The Application of Spinors to Pulse Synthesis and Analysis", Journal of Magnetic Resonance in Medicine, vol. 12, pp. 93-98 (1989).
M. Shinnar et al., "The Use of Finite Impulse Response Filters in Pulse Design", Journal of Magnetic Resonance in Medicine, vol. 12, pp. 81-87 (1989).
M. Shinnar et al., "The Synthesis of Pulse Sequences Yielding Arbitrary Symmetric Magnetization Vectors", in Journal of Magnetic Resonance, vol. 72, pp. 298-306.
M. Shinnar et al., "The Synthesis of Soft Pulses with a Specified Frequency Response", Journal of Magnetic Resonance in Medicine, vol. 12, pp. 88-92 (1989).
M. S. Silver et al., "Highly Selective .pi./2 and .pi. Pulse Generation", Journal of Magnetic Resonance, vol. 59, pp. 347-351 (1984).
V. H. Subramanian et al., "An Exact Synthesis Procedure for Frequency Selective Pulses", in 5th Proceedings of the Magnetic Resonance in Medicine, pp. 1452-1453, Aug., 1986.
H. Yan and J. C. Gore, "Improved Selective 180.degree. Radiofrequency Pulses for Magnetization Inversion and Phase Reversal", Journal of Magnetic Resonance, vol. 71, pp. 116-131 (1987).
Leigh John S.
Shinnar Meir
Tokar Michael J.
Trustees of the University of Penna.
LandOfFree
Methods of generating pulses for selectively exciting frequencie does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods of generating pulses for selectively exciting frequencie, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods of generating pulses for selectively exciting frequencie will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1191976