Method and system for controlling characteristics of gradient ma

Details Method and system for controlling characteristics of gradient ma Method and system for controlling characteristics of gradient ma

1988-03-14

1989-08-29

Tokar, Michael J.

Electricity: measuring and testing

Particle precession resonance

Using a nuclear resonance spectrometer system

324307, 324318, G01R 3320

Patent

active

048620840

ABSTRACT:
In MRI, in order to provide accurate position data of a subject to an MR signal, the characteristics of the gradient magnetic fields are controlled. The characteristics, i.e., rise time T.sub.r of the waveform of a current signal required in generating a gradient magnetic field is described as: T.sub.r =(Z.sub.l /Z.sub.r) ln (V/V-I.sub.out .multidot.Z.sub.r)), where Z.sub.l is an inductance part of a gradient field generating coil, Z.sub.r is a resistance part of a gradient field generating coil, V is a power source voltage of a gradient field generating power source, and I.sub.out is a current supplied to the gradient field generating coil. As impedances of the gradient field generating coils are different from one another, the characteristics, for example, rise time periods, of the gradient magnetic fields are controlled by regulating the power source voltage of a gradient magnetic field generating power source. The characteristics of the gradient magnetic fields are also controlled by making trapezoidal waves.

REFERENCES:
patent: 4644278 (1987-02-01), Sauo et al.
patent: 4703275 (1987-10-01), Holland
patent: 4728890 (1988-03-01), Pattany et al.
patent: 4742311 (1988-05-01), Van der Zwart
patent: 4761613 (1988-08-01), Hinks
RCA Transistor, Thryistor, and Diode Manual, RCA Solid State Division, Somerville, N.J., 1971, p. 65.

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