永磁磁共振成像系统磁体的梯度匀场方法研究

Gradient Shimming in Magnetic Resonance Imaging Magnet

摘要: 利用梯度线圈进行永磁磁共振成像系统中主动匀场,采用改变梯度线圈电流的方法改善系统中主磁场的均匀性,提出了简单实用的共振峰半高宽测试法作为匀场判断标准. 实验结果表明:半高宽法是判断匀场效果的基本方法,梯度匀场方法在不改变系统硬件的基础上进行主动匀场,匀场效果可以满足一般成像精确度的要求. 该方法已在研制的0.4T永磁磁共振成像系统主动匀场中取得了较好的效果.

Abstract: A gradient shimming method is presented to promote the homogeneity, and the full width at half maximum (FWHM) of the resonance line is used to measure the effect of gradient shimming. Results of experiments, showed the FWHM as a basic criterion for gradient shimming, which has worked efficiently in the 0.4 T magnetic resonance imaging(MRI) scanner.