Shen J, Rycyna R E, Rothman D L
Magnetic Resonance Center, Yale University, School of Medicine, New Haven, CT 06510, USA.
Magn Reson Med. 1997 Nov;38(5):834-9. doi: 10.1002/mrm.1910380521.
Improvements on a localized, automatic shimming method described by Gruetter and Boesch (J. Magn. Reson. 96, 323-334 (1992)) and Gruetter (Magn. Reson. Med. 29, 804-811 (1993)) are presented. A spin-echo sequence employing a double sech refocusing scheme is used to acquire a field map along linear projections that improves the signal-to-noise ratio by at least a factor of two over the stimulated echo sequence previously used. To further improve the reliability of shim adjustments, a variance-weighted polynomial regression analysis is performed. This also extends the scope of application of this technique to global shimming. Localized 1H spectra of human brain shimmed by this method are presented.
本文介绍了对Gruetter和Boesch（《磁共振杂志》96卷，323 - 334页，1992年）以及Gruetter（《磁共振医学》29卷，804 - 811页，1993年）所描述的局部自动匀场方法的改进。采用双sech重聚焦方案的自旋回波序列用于沿线性投影获取场图，与之前使用的受激回波序列相比，该方法将信噪比提高了至少两倍。为了进一步提高匀场调整的可靠性，进行了方差加权多项式回归分析。这也将该技术的应用范围扩展到了全局匀场。展示了用此方法匀场后的人脑局部1H谱。
