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Fast analytical calculation method for eddy current induced by gradient fields in an MRI system

Zheng Xu (State Key Laboratory of Power Transmission Equipment and System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, China)
Jiamin Wu (State Key Laboratory of Power Transmission Equipment and System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, China)
Lu Li (State Key Laboratory of Power Transmission Equipment and System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, China)
Yucheng He (State Key Laboratory of Power Transmission Equipment and System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, China)
Wei He (State Key Laboratory of Power Transmission Equipment and System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, China)
Dengjie Yu (State Key Laboratory of Power Transmission Equipment and System Security and New Technology, School of Electrical Engineering, Chongqing University, Chongqing, China)
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Abstract

Purpose

Eddy currents are inevitable in magnetic resonance imaging (MRI) systems. These currents are mainly induced by gradient fields. This study aims to propose a fast analytical method to calculate eddy currents induced by frequently switching gradient fields in a traditional C-shape MRI system.

Design/methodology/approach

Fourier decomposition and magnetic vector potentials were used to calculate the eddy currents. Calculations with the proposed analytical method revealed the spatial distribution and temporal evolution of eddy currents.

Findings

Calculation and Maxwell simulation results were consistent. The agreement between calculation and simulation results indicates that increasingly sophisticated structures could be developed. The calculated results could guide the design of improved gradient coils.

Originality/value

Eddy currents induced by gradient current are decomposed into currents induced by each time-harmonic component, and then adding them together to obtain complete contribution of the eddy current. The analytical method was used to characterize the properties of symmetric and asymmetric eddy currents induced by gradient coils in MRI systems. The analytical method can be used to improve the gradient shield during the design of the gradient coil in the MRI system.

Keywords

Acknowledgements

This work was supported by the State Key Development Program for Basic Research of China (973 Project, No. 2014CB541602), the National Natural Science Foundation of China (No. 51377182, 51677008 and 11647098), Scientific Research Foundation of State Key Laboratory of Power Transmission Equipment and System Security (No. 2007DA10512713103) and Fundamental Research Funds of Central Universities (No. 106112017CDJQJ158834).

Citation

Xu, Z., Wu, J., Li, L., He, Y., He, W. and Yu, D. (2017), "Fast analytical calculation method for eddy current induced by gradient fields in an MRI system", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 36 No. 6, pp. 1690-1705. https://doi.org/10.1108/COMPEL-12-2016-0566

Publisher

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Emerald Publishing Limited

Copyright © 2017, Emerald Publishing Limited

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