Measurement and calibration of eddy currents for magnetic resona

Details Measurement and calibration of eddy currents for magnetic resona Measurement and calibration of eddy currents for magnetic resona

1989-04-27

1990-12-18

Tokar, Michael J.

Electricity: measuring and testing

Particle precession resonance

Using a nuclear resonance spectrometer system

324318, G01R 3320

Patent

active

049789198

ABSTRACT:
A sample (80) is disposed in an examination region (10) through which a strong, uniform magnetic field is generated. A gradient pulse (24, 82) is created across the magnetic field. After the gradient field has been turned off, a rapid succession of radio frequency pulses (52, 84) are applied. Each radio frequency pulse is followed by a free induction decay signal (54, 86). For each free induction decay signal, the evolution of phase vs. time is determined (60) because the slope of the changing phase vs. changing time curve is proportional to resonance frequency (66) and the resonance frequency is proportional to magnetic field strength (68). For each free induction decay signal, the magnetic field strength and the time since the determination of the gradient field pulse are determined and stored (70). From the plurality of free induction decay signals, a decaying curve (28) representing eddy current induced gradient field strength vs. time is produced.

REFERENCES:
patent: 4698591 (1987-10-01), Glover et al.
patent: 4818942 (1989-04-01), Rzedzian
patent: 4823084 (1989-04-01), McKinnen
"Measurement of Magnetic Field Gradient by its Effect on the NMR Free Induction Decay" by James S. Murday, Journal of Mag. Res., 10, pp. 111-120, 1973.
"Exact Temporal Eddy Current Compensation in Magnetic Resonance Imaging Systems" by Morich et al., IEEE Transaction on Medical Imaging, vol. 7, No. 3, Sep. 1988, pp. 247-254.
"Gradient Time-Shape Measurement by NMR" by Yamamoto et al., J. Phys. E. Sci. Instrum., 19, pp. 708-711, 1986.

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