Analysis of eddy currents induced by transverse and longitudinal gradient coils in different tungsten collimators geometries for SPECT/MRI integration

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.

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Mitigation of Intra-coil Eddy Currents in Split Gradient Coils in a Hybrid MRI-LINAC System

IEEE Transactions on Biomedical Engineering ◽

10.1109/tbme.2016.2573316 ◽

2016 ◽

pp. 1-1 ◽

Cited By ~ 1

Author(s):

Fangfang Tang ◽

Fabio Freschi ◽

Maurizio Repetto ◽

Yu Li ◽

Feng Liu ◽

...

Keyword(s):

Eddy Currents ◽

Gradient Coils

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Longitudinal gradient coils with enhanced radial uniformity in restricted diameter: Single-current and multiple-current approaches

Journal of Magnetic Resonance ◽

10.1016/j.jmr.2017.01.012 ◽

2017 ◽

Vol 276 ◽

pp. 69-77 ◽

Cited By ~ 5

Author(s):

Javier A. Romero ◽

Gabriela A. Domínguez ◽

Esteban Anoardo

Keyword(s):

Gradient Coils ◽

Longitudinal Gradient

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The design of cylindrical longitudinal gradient coils with simulated annealing

2016 IEEE International Conference on Computational Electromagnetics (ICCEM) ◽

10.1109/compem.2016.7588619 ◽

2016 ◽

Author(s):

L. Li ◽

Z. H. Zhu ◽

X.W. Ping

Keyword(s):

Simulated Annealing ◽

Gradient Coils ◽

Longitudinal Gradient

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Design, Characterisation and Performance of an Improved Portable and Sustainable Low-Field MRI System

Frontiers in Physics ◽

10.3389/fphy.2021.701157 ◽

2021 ◽

Vol 9 ◽

Author(s):

Bart de Vos ◽

Javad Parsa ◽

Zaynab Abdulrazaq ◽

Wouter M. Teeuwisse ◽

Camille D. E. Van Speybroeck ◽

...

Keyword(s):

Eddy Currents ◽

Point Of Care ◽

Low Frequency ◽

Gradient Coils ◽

Rf Amplifier ◽

Target Field ◽

Low Field ◽

Gradient Amplifier ◽

And Performance

Low-field permanent magnet-based MRI systems are finding increasing use in portable, sustainable and point-of-care applications. In order to maximize performance while minimizing cost many components of such a system should ideally be designed specifically for low frequency operation. In this paper we describe recent developments in constructing and characterising a low-field portable MRI system for in vivo imaging at 50 mT. These developments include the design of i) high-linearity gradient coils using a modified volume-based target field approach, ii) phased-array receive coils, and iii) a battery-operated three-axis gradient amplifier for improved portability and sustainability. In addition, we report performance characterisation of the RF amplifier, the gradient amplifier, eddy currents from the gradient coils, and describe a quality control protocol for the overall system.

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