MAGNETIC-FIELD MAPPING WITH AN ARRAY OF NUCLEAR-MAGNETIC-RESONANCE PROBES

Magnetic field maps can rapidly and accurately be acquired on the surf ace of a cylinder or sphere with an array of nuclear magnetic resonanc e (NMR) coils multiplexed to a single radiofrequency receiver. Using a n array of NMR probes significantly decreases the time necessary to ma p B-0 and improves field map accuracy because the probes do not move. The spatial variation of the Larmor frequency is used to determine the spherical harmonic components present in the held. A limitation of th is approach is that NMR resonant circuits are inherently narrow band w hich limits the apparatus to a specific field strength and only points in space defined by the array layout. This apparatus can characterize the magnetic fields of high homogeneity dipole magnets, quadrupole ma gnets, gradient coils, and shims used in NMR imaging systems. (C) 1996 American Institute of Physics.