Improved Strategy and Experimental Research on Passive Shimming in Magnetic Resonance Imaging Magnet
Qu Hongyi1,2, Liu Xin2,3, Wang Hui1, Liu Jianhua1,2, Wang Qiuliang1,2,3
1. Institute of Electrical Engineering Chinese Academy of Science Beijing 100190 China; 2. Ganjiang Innovation Academy Chinese Academy of Sciences Ganzhou 341000 China; 3. College of Rare Earths University of Science and Technology of China Hefei 230026 China
Abstract：Passive shimming is used to correct the inhomogeneous magnetic field of the MRI magnets. Due to the inevitable calculation errors, passive shimming must be repeated many times (iteration) to obtain a required high homogeneous static magnetic field. At present, the relevant research mainly focuses on constructing the optimization model or improving the solution algorithm. The research method is usually the numerical simulation method, ignoring the problems encountered in the shimming practice, and there is no optimization based on the shimming process. To improve the performance and efficiency of shimming, this paper presented an improved strategy for the passive shimming technology in MRI magnets: measuring the actual magnetic field of multiple representative pieces to correct the calculation; constructing a linear optimization model with the target magnetic field as a variable; adopting “Odd-Even” approach to simplify the assembly of the shim system. Finally, the experiment for the improved shimming technology was performed on a 1.5T MRI superconducting magnet. The results show that the magnetic field homogeneity that meets the imaging requirements could be obtained only through two iterations, and the design value was reached after the third iteration. Compared with the results of the method before improvement, the new shimming strategy has a significant effect.
曲洪一, 刘鑫, 王晖, 刘建华, 王秋良. 磁共振成像磁体无源匀场改进策略及实验研究[J]. 电工技术学报, 2022, 37(24): 6284-6293.
Qu Hongyi, Liu Xin, Wang Hui, Liu Jianhua, Wang Qiuliang. Improved Strategy and Experimental Research on Passive Shimming in Magnetic Resonance Imaging Magnet. Transactions of China Electrotechnical Society, 2022, 37(24): 6284-6293.
[1] 冯焕, 姜晖, 王雪梅. 功能磁共振成像在肿瘤学领域的应用[J]. 电工技术学报, 2021, 36(4): 705-716. Feng Huan, Jiang Hui, Wang Xuemei.Application of functional magnetic resonance imaging in the field of oncology[J]. Transactions of China Electrotechnical Society, 2021, 36(4): 705-716. [2] 李晓南, 任雯廷, 刘国强, 等. 高分辨率磁共振电特性成像及脑肿瘤诊断初步研究[J]. 电工技术学报, 2021, 36(18): 3860-3866. Li Xiaonan, Ren Wenting, Liu Guoqiang, et al.Preliminary conductivity reconstruction by high- resolution magnetic resonance electrical properties tomography for brain tumor diagnosis[J]. Transa- ctions of China Electrotechnical Society, 2021, 36(18): 3860-3866. [3] 张西亚. 磁场均匀度对MR图像质量的影响[J]. 生物医学工程与临床, 2008, 12(3): 245-248. Zhang Xiya.The effect of magnetic field homogenous level on the quality of MRI[J]. Biomedical Engin- eering and Clinical Medicine, 2008, 12(3): 245-248. [4] 王秋良. 磁共振成像系统的电磁理论与构造方法[M]. 北京: 科学出版社, 2018. [5] Belov A, Bushuev V, Emelianov M, et al.Passive shimming of the superconducting magnet for MRI[J]. IEEE Transactions on Applied Superconductivity, 1995, 5(2): 679-681. [6] Frollo I, Andris P, Strolka I.Measuring method and magnetic field homogeneity optimization for magnets used in NUM-imaging[J]. Measurement Science Review, 2001,1(1): 9-12. [7] Tang Wenju, Wang Hui, Li Yi, et al.An accurate passive shimming method[C]//8th International Con- ference on Information Technology in Medicine and Education (ITME), Fuzhou, China, 2016: 66-69. [8] Abe M, Sakakibara K, Fujikawa T, et al.Static magnetic field shimming calculation using TSVD regularization with constraints of iron piece place- ments[J]. IEEE Transactions on Applied Super- conductivity, 2017, 27(7): 1-12. [9] Kong Xia, Zhu Minhua, Xia Ling, et al.Passive shimming of a superconducting magnet using the L1-norm regularized least square algorithm[J]. Journal of Magnetic Resonance, 2016, 263: 122-125. [10] Qu Hongyi, Niu Chaoqun, Wang Yaohui, et al.The optimal target magnetic field method for passive shimming in MRI[J]. Journal of Superconductivity and Novel Magnetism, 2020, 33(3): 867-875. [11] Zhu Xuchen, Wang Houshen, Wang Hui, et al.A novel design method of passive shimming for 0.7T biplanar superconducting MRI magnet[J]. IEEE Transactions on Applied Superconductivity, 2016, 26(7): 1-5. [12] 武海澄, 刘正敏, 周荷琴. 磁共振成像永磁体的无源匀场方法[J]. 电工技术学报, 2007, 22(11): 7-11. Wu Haicheng, Liu Zhengmin, Zhou Heqin.Research on passive shimming method for MRI permanent magnet[J]. Transactions of China Electrotechnical Society, 2007, 22(11): 7-11. [13] You Xiaofei, Wang Zheng, Zhang Xiaobing, et al.Passive shimming based on mixed integer pro- gramming for MRI magnet[J]. Science China Tech- nological Sciences, 2013, 56(5): 1208-1212. [14] Zhang Yanli, Xie Dexin, Bai Baodong, et al.A novel optimal design method of passive shimming for permanent MRI magnet[J]. IEEE Transactions on Magnetics, 2008, 44(6): 1058-1061. [15] So N.Formulation of the spherical harmonic coefficients of the entire magnetic field components generated by magnetic moment and current for shimming[J]. Journal of Applied Physics, 2014, 115(16): 163908. [16] Liu Feng, Zhu Jianfeng, Xia Ling, et al.A hybrid field-harmonics approach for passive shimming design in MRI[J]. IEEE Transactions on Applied Superconductivity, 2011, 21(2): 60-67. [17] Furlani E P.Electromechanical devices[M]// Amsterdam: Elsevier, 2001: 335-467. [18] 潘子君, 潘成, 唐炬, 等. 基于图像复原技术与约束最小二乘方滤波器的绝缘子表面电荷反演算法[J]. 电工技术学报, 2021, 36(17): 3627-3638. Pan Zijun, Pan Cheng, Tang Ju, et al.Inversion algorithm for surface charge on insulator based on image restoration technology and constrained least square filter[J]. Transactions of China Electro- technical Society, 2021, 36(17): 3627-3638. [19] Qu Hongyi, Wang Yaohui, Niu Chaoqun, et al.A novel strategy and test of passive shimming for multi-volumes in cylindrical MRI scanner[J]. IEEE Transactions on Magnetics, 2020, 56(2): 1-7. [20] 袁佳歆, 曲锴, 郑先锋, 等. 高速铁路混合储能系统容量优化研究[J]. 电工技术学报, 2021, 36(19): 4161-4169, 4182. Yuan Jiaxin, Qu Kai, Zheng Xianfeng, et al.Optimizing research on hybrid energy storage system of high speed railway[J]. Transactions of China Electrotechnical Society, 2021, 36(19): 4161-4169, 4182. [21] 李少岩, 任乙沛, 顾雪平, 等. 基于短路电流约束显式线性建模的输电网结构优化[J]. 电工技术学报, 2020, 35(15): 3292-3302. Li Shaoyan, Ren Yipei, Gu Xueping, et al.Optimization of transmission network structure based on explicit linear modeling of short circuit current constraints[J]. Transactions of China Electrotechnical Society, 2020, 35(15): 3292-3302. [22] 曲洪一. 高场磁共振成像主磁体电磁优化方法研究[D]. 北京: 中国科学院大学, 2020. [23] Ping Xuewei, Wang Mingyu, Yin Xinghui, et al.Evaluation of VRMS homogeneity of the magnetic field in MRI with numerical methods[C]//International Applied Computational Electromagnetics Society Symposium-China (ACES), Nanjing, China, 2019: 1-2.
2022, Vol. 37 
