核磁共振成像磁体的有源匀场技术

Active Shimming Technique of NMR Imaging Magnet

介绍一种算法用于核磁共振成像磁体的有源匀场,根据有源匀场的原理和方法,从Maxwell基本场理论出发,应用球谐函数建立磁场分布模型,针对模型中的不均匀场分量,设计相对应的各种相互独立的匀场线圈,通过该算法求得各匀场线圈中的补偿电流。该算法简捷实用,根据所建立的算法设计的匀场软件SHIM通用性强,使用方便,可应用于各类磁体的有源匀场,其效率在LMW-400型常导磁体上得到证实并获得推广应用。

An algorithm used'in active shimming of NMR imaging magnet is proposed. From Maxwell's equations, the magnetic field is analysed using spherical harmonics. Shim coils are designed to correct magnetic field homogeneity. As each shim coil generated field gradient is mutually independent, shimming field become easy. The SHIM program using this algorithm can be applied to various magnets adopting active shimming, its efficiency has been tested and confirmed with LMW-400 magnet,