Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1994-07-28
1996-11-05
O'Shea, Sandra L.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324307, 324309, G01V 300, G01V 314
Patent
active
055721265
ABSTRACT:
A technique has previously been described for generating optimal RF pulse sequences using finite impulse response filter techniques to calculate the Fourier series which would yield the desired z and xy magnetizations in a magnetic resonance imaging device. Such a technique is now extended to allow for control of the input pulse shape as well as the frequency response. Since the peak power is limited by the amplifier power and the total energy of the pulse is limited by the specific absorption rate (SAR) of the tissue or sample, it is desired to limit the peak power and total energy of the input pulse without degrading the resulting excitation. This is accomplished by recognizing that the total energy of the pulse is encoded in the lowest order Fourier series coefficients of the frequency response and then specifying the total energy of the pulse as a design parameter to the RF pulse synthesis algorithm. Peak power of the pulse may also be limited by selecting roots for .beta.(.omega.), where M.sub.z (.omega.)=.linevert split..alpha.(.omega.).linevert split..sup.2 -.linevert split..beta.(.omega.).sup.2, which leads to pulses with variable phase yet do not change the overall frequency response. By appropriately selecting .alpha.(.omega.) and .beta.(.omega.), a hard pulse sequence is generated which serves as the basis for a shaped pulse which meets the desired constraints on the input pulse shape.
REFERENCES:
patent: 5153515 (1992-10-01), Leigh et al.
patent: 5280245 (1994-01-01), Pauly
J. W. Carlson, "Exact Solutions for Selective-Excitation Pulses", Journal of Magnetic Resonance 94, 1991, pp. 376-386.
S. Conolly, "Optimal Control Solutions to the Magnetic Resonance Selective Excitation Problem", IEEE Transactions on Medical Imaging, vol. MI-5, No. 2, Jun. 1986, pp. 106-115.
S. M. Eleff, "The Synthesis of Pulse Sequences Yielding Arbitrary Symmetric Magnetization Vectors", Journal of Magnetic Resonance 72, 1987, pp. 298-306.
S. D. McDonald, "Testing the Limits of Shape Optimization by Large-Flip-Angle Pulses" Journal of Magnetic Resonance 99, 1992, pp. 282-291.
J. Pauly, "Parameter Relations for the Shinnar-LeRoux Selective Excitation Pulse Design Algorithm", IEEE Transactions on Medical Imaging, vol. 10, No. 1, Mar. 1991, pp. 53-65.
D. E. Rourke, "The Inverse Scattering Transform and Its Use in the Exact Inversion of the Bloch Equation for Noninteracting Spins", Journal of Magnetic Resonance 99, 1992, pp. 118-138.
M. Shinnar, "Notes: Frequency Response of Soft Pulses", Journal of Magnetic Resonance 75, 1987, pp. 502-505.
M. Shinnar, "Inversion of the Bloch Equation", J. Chem. Phys., vol. 98, No. 8, Apr. 15, 1993, pp. 6121-6128.
M. Shinnar, "The Application of Spinors to Pulse Synthesis and Analysis", Magnetic Resonance in Medicine 12, 1989, pp. 93-98.
M. Shinnar, "The Synthesis of Soft Pulses with a Specified Frequency Response", Magnetic Resonance in Medicine 12, 1989, pp. 88-92.
M. Shinnar, "The Use of Finite Impulse Response Filters in Pulse Design", Magnetic Resonance in Medicine 12, 1989 pp. 81-87.
A. E. Yagle, "Inversion of the Bloch Transform in Magnetic Resonance Imaging Using Asymmetric Two-Component Inverse Scattering", Inverse Problems 6, 1990, pp. 133-151.
M. Shinnar, "The Synthesis of Pulse Sequences Yielding Arbitrary Magnetization Vectors", Magnetic Resonance in Medicine 12, 1989, pp. 74-80 .
Haynes Mack
O'Shea Sandra L.
University of Pennsylvania
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