Apparatus and method for stabilizing the background magnetic fie

Details Apparatus and method for stabilizing the background magnetic fie Apparatus and method for stabilizing the background magnetic fie

1991-05-20

1993-09-14

Tokar, Michael J.

Electricity: measuring and testing

Particle precession resonance

Spectrometer components

G01R 3320

Patent

active

052452867

ABSTRACT:
A pair of serially-connected coils detect noise variations in an MRI background magnetic field. Although the coils are closely coupled to the primary background magnetic field generator of the MRI system, they are disposed so as to be substantially de-coupled from rapidly changing MRI gradient magnetic fields. The noise detecting loops drive a negative feedback loop including a low pass filter, amplifier and controlled current source driving a large correcting loop. The device attenuates background magnetic field noise during MRI data acquisition over a frequency band extending from a few millihertz to more than 100 Hz. It is preferably used with existing field stabilization software that otherwise compensates for fluctuations in an overlapping frequency band which starts at d.c. Thus, when used together, background magnetic field noise may be attenuated (or compensated for in subsequent MRI data processing) over a frequency band that extends from d.c. to more than 100 Hz.

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Pohjonen, et al, "Compensation of Magnetic Field Instabilities in MRI", SMRM Eighth Annual Meeting (Amsterdam 1989) p. 968.

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