一种永磁磁共振中磁体涡流场的测量方法

摘要

Magnetic resonance imaging (MRI) is a widely used medical imaging technique.In MRI system,gradient magnetic fields are used to code spatial information.However,the fast-switching electric currents in the gradients coils used to generate gradient fields also induce vortex electric field,often referred as eddy current,in the surrounding metal conductors.In this paper,a method for eddy current field measurement was proposed.Based on the Faraday law of electromagnetic induction,an eddy current field measuring device was designed.Combining hardware acquisition and software processing,the eddy current field was obtained by subtracting the ideal gradient field from the magnetic field measured experimentally,whose waveform could be displayed in real time.The proposed method was verified by experimental results.%磁共振成像(Magntic Resonance Imaging,MRI)技术是一种先进的医疗影像技术.在MRI系统中,通过梯度线圈电流快速切换方向,对待测区域施加梯度磁场,产生的梯度磁场会在其周围的金属体内激发出变化的涡旋电场,进而导致金属体内闭合的回路中产生对原来的梯度电流起抑制作用的感生电流,也就是我们所说的涡流.本文介绍了一种测量磁体涡流场的方法,结合电磁感应定律,设计了一种磁体涡流场测量装置,通过硬件采集以及软件处理的方法,将理想梯度场与实际磁场进行相减并将波形实时呈现,实验结果表明该方法可实现对磁体涡流场的测量.