The magnetic field homogeneity is an important indicator of magnetic resonance imaging (MRI) magnets. This paper presents a magnetic field homogeneity measuring system that is suitable for regular testing and inhomogeneities correction of MRI magnets. The system is based on the nuclear magnetic resonance (NMR) method and on spherical harmonic expansion to realize the detection of magnetic field and the calculation of the inhomogeneity respectively. A probe array and a spatial positioning device are adopted to detect the magnetic field intensity within a diameter range of 50 cm from the center of the MRI magnet. To control the system, a software with LabVIEW is designed.

MRI;Magnetic Field Homogeneity;Magnetic Field Measurement