Finite element method-based approach for radiofrequency magnetic resonance coil losses estimation

IF 0.9 4区 医学 Q4 CHEMISTRY, PHYSICAL Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2017-01-31 DOI:10.1002/cmr.b.21348
Giulio Giovannetti, Gianluigi Tiberi, Michela Tosetti
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引用次数: 7

Abstract

The simulation and the design of radiofrequency (RF) coils are fundamental tasks to maximize Signal-to-Noise Ratio (SNR) in Magnetic Resonance (MR) applications. The estimation of coil resistance, that is, the losses within the coil conductors, which depends on tuning frequency, allows the prediction of coil performance and data SNR. At RF, the conductor resistance is increased due to the skin effect, which distributes the current primarily near the conductor surface instead of uniformly over the cross section. Moreover, the radiative losses estimation as a function of tuning frequency permits a total coil performance characterization, especially for high-frequency tuned coils when this loss mechanism could be the dominant one. In this work we compared Finite Element Method (FEM) simulations with analytical calculations performed in wire loop RF coils for MR applications. Our results showed that FEM can predict the losses within the coil conductors at 5.7 MHz with a relative difference of <3% compared to analytical calculation, while the relative difference increased to 58% at 127.8 MHz. Concerning the radiative losses, the relative difference between analytical formulation and FEM was lower than 3% at 5.7 MHz, and increasing to 44% at 127.8 MHz. Experimental measurements on a circular coil prototype were also performed at 85.2 MHz and 127.8 MHz, showing a better agreement with FEM simulations than with analytical calculations.

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基于有限元法的射频磁共振线圈损耗估算方法
射频(RF)线圈的仿真和设计是磁共振(MR)应用中最大化信噪比(SNR)的基本任务。线圈电阻的估计,即线圈导体内的损耗,取决于调谐频率,可以预测线圈性能和数据信噪比。在射频下,由于趋肤效应,导体电阻增加,趋肤效应使电流主要分布在导体表面附近,而不是均匀地分布在截面上。此外,作为调谐频率函数的辐射损耗估计允许对线圈的总体性能进行表征,特别是对于高频调谐线圈,当这种损耗机制可能占主导地位时。在这项工作中,我们比较了有限元法(FEM)模拟与在磁流变应用的线圈环射频线圈中进行的分析计算。结果表明,在5.7 MHz时,有限元法可以预测线圈导体内部的损耗,与分析计算的相对差值为3%,而在127.8 MHz时,相对差值增加到58%。在5.7 MHz时,解析公式与有限元法的相对差异小于3%,在127.8 MHz时,两者的相对差异增大到44%。在85.2 MHz和127.8 MHz频率下对圆形线圈样机进行了实验测量,结果表明有限元模拟结果比解析计算结果更吻合。
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来源期刊
CiteScore
2.60
自引率
0.00%
发文量
3
审稿时长
>12 weeks
期刊介绍: Concepts in Magnetic Resonance Part B brings together engineers and physicists involved in the design and development of hardware and software employed in magnetic resonance techniques. The journal welcomes contributions predominantly from the fields of magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR), but also encourages submissions relating to less common magnetic resonance imaging and analytical methods. Contributors come from both academia and industry, to report the latest advancements in the development of instrumentation and computer programming to underpin medical, non-medical, and analytical magnetic resonance techniques.
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