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磁场的均匀性是磁共振系统的重要指标，随着一些先进的核磁共振扫描成像技术如ＭＰＲ、ＭＩＲ。ＥＰＩ等的出现，对磁场的均匀度也提出了更高的要求。核磁共振系统匀场的方法有两种，即无源匀场和有源匀场。而无源匀场是基础，其结果是永久性的，没有达到理想的无源匀场效果，
The homogeneity of the magnetic field is an important indicator of the magnetic resonance system, along with some advanced nuclear magnetic resonance imaging techniques such as MPR and MIR. The emergence of EPI, etc., also put forward higher requirements for the uniformity of the magnetic field. There are two ways to shimming the MRI system, passive shimming and active shimming. The passive shimming is the basis. The result is permanent and does not achieve the ideal passive shimming effect.