磁共振成像中取向硅钢片饱和磁化强度测定方法
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摘要
该文提出一种适于工程应用的取向硅钢片饱和磁化强度测定方法。将硅钢片放入待匀场梯度线圈的匀场轨道中,利用磁场测量设备测量出采样点处硅钢片产生的纵向磁感应强度,将测量结果通过迭代算法优化,即可计算出取向硅钢片的饱和磁化强度。结果表明,将饱和磁化强度计算结果用于磁共振成像系统无源匀场时,提高了成像质量。该方法在实际应用中方便易行,无需大量计算,效率较高。
A measuring method of saturation magnetization for oriented silicon steel sheets in engineering application is proposed here. Silicon steel sheets are placed into the shim rails distributed on the gradient coils and the axial magnetization of sampling points is measured through using the magnet field camera. The saturation magnetization of grain-oriented silicon steel sheets is obtained by iterative optimization algorithms. The result of the saturation magnetization can make the passive shimming of the magnetic resonance imaging system more efficient and improve the imaging quality. The method is convenient and easy for practice use. It needs less computation load and is more efficient.
A measuring method of saturation magnetization for oriented silicon steel sheets in engineering application is proposed here. Silicon steel sheets are placed into the shim rails distributed on the gradient coils and the axial magnetization of sampling points is measured through using the magnet field camera. The saturation magnetization of grain-oriented silicon steel sheets is obtained by iterative optimization algorithms. The result of the saturation magnetization can make the passive shimming of the magnetic resonance imaging system more efficient and improve the imaging quality. The method is convenient and easy for practice use. It needs less computation load and is more efficient.
引文
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[2] Doni B,Vermilyea M E,Toffolo W E. Passive shimming of MR magnets:Algorithm,hardware,and results[J]. IEEE Transactions on Applied Superconductivity,1993,3(1):254-257.
[3] Liu Feng,Zhu Jianfeng,Xia Ling,et al. A hybrid fieldharmonics approach for passive shimming design in MRI[J]. IEEE Transactions on Applied Superconductivity,2011,21(2):60-67.
[4] Kotnala R K,Kothari P C. Magnetic measurements on electrical steel strips using standard Epstein frame[J].Indian Journal of Pure&Applied Physics,2000,38:797-800.
[5] Kockar H,Meydan T. Specific power loss comparisons of magnetic strips using standard Epstein frame[J].Journal of the Korean Physical Society,2002,40(5):918-920.
[6]张俊鹏,张晗,向前,等.电工钢方圈磁性测量偏差影响因素的探讨[J].钢铁研究,2017,45(4):38-41.Zhang Junpeng,Zhang Han,Xiang Qian,et al. Discussion on influence factors of magnetic measurement deviation of electrical steel by Epstein frame[J].Research on Iron and Steel,2017,45(4):38-41.
[7] Ping Xiewei,Zhu Zihui,Yin Xinhui,et al. Finite element simulation of eddy currents induced by gradient coils in superconducting MRI[C]//Proceedings of IEEE International Conference on Computational Electromagnetics. Guangzhou,China:IEEE,2016:37-39.
[8] Hu Yang,Wang Qiuliang,Hu Xinning,et al. A simulation study on the design of gradient coils in MRI for the imaging area above the patient bed[J]. Measurement Science&Technology,2017,28(3):035402.
[9] Jia F,Schultz G,Testud F,et al. Performance evaluation of matrix gradient coils[J]. Magnetic Resonance Materials in Physics Biology&Medicine,2016,29(1):59-73.
[10] Romeo F,Hoult D I. Magnet field profiling:Analysis and correcting coil design[J]. Magnetic Resonance in Medicine,1984,1(1):44-65.
[11] Hoult D I,Lee D. Shimming a superconducting nuclear magnetic resonance imaging magnet with steel[J].Review of Scientific Instruments,1985 56(1):131-135.
[12] Jackson J D. Classical electrodynamics[M]. New York,US:Wiley,1975.