Abstract
This paper focuses on radiofrequency (RF) coils that can produce a high electromagnetic field homogeneity to be used for magnetic resonance imaging (MRI) applications. The proposed structure is composed of four wire loops symmetrically located on an ellipsoidal surface. The main objective of this work is to improve field homogeneity compared to a standard Helmholtz coil. Numerical simulation was carried out to assess the RF electromagnetic field behavior of the proposed coil. Different electrical modeling and simulations were investigated, particularly the study of the whole modeling of the proposed structure taking into account all the couplings between the loops. The proposed coil was evaluated and compared with the standard Helmholtz coil. Simulation and experimental results confirmed the good performance of the developed coil in terms of electromagnetic field homogeneity, efficiency, sensitivity, and quality factor.
Highlights
Since the demonstration of the nuclear magnetic resonance (NMR) phenomenon in 1946, the number of its applications grows steadily [1,2,3]
For RF coils that do not have a specific periodicity, optimization and implementation are more challenging. This is the case of Helmholtz coils [13] which consist of two coaxial circular coils separated by a distance equal to their radius
This work, which includes modeling, simulations and experimental results, intends to be an important input for RF coils resulting from Helmholtz structure which can be used for magnetic resonance imaging (MRI) applications
Summary
Since the demonstration of the nuclear magnetic resonance (NMR) phenomenon in 1946, the number of its applications grows steadily [1,2,3]. This research work considers aspects related to electronic instrumentation and in particular, the design, modeling and optimization of RF coils for magnetic resonance imaging, presenting a certain simplicity of implementation and having good homogeneity of RF electromagnetic field. The optimization and modeling of a symmetrical coil with four coaxial circular loops producing effective sixth order homogeneity of electromagnetic field are presented. The main objective is to increase the sensitivity of the coil and reduce the number of tuned loops from four to two, which can be done by connecting the two loops positioned in the same side in series with a shared tuning capacitance This configuration looks like a distributed Helmholtz coil. This work, which includes modeling, simulations and experimental results, intends to be an important input for RF coils resulting from Helmholtz structure which can be used for MRI applications
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