Spherical and Improved Helmholtz Coil with High B&lt;sub&gt;1&lt;/sub&gt; Homogeneity for Magnetic Resonance Imaging

The design and testing of a Helmholtz prototype probe with a relatively homogeneous radiofrequency field that can be used for MRI are presented in this paper. It consists of two coaxial separately tuned ellipsoidal rings of wire in a symmetric arrangement. The developed ellipsoidal structure is tested experimentally in free space and is compared with the results obtained with an equivalent circular standard Helmholtz coil. Complete electrical modeling of the coils taking into account all couplings (inductive and capacitive) is studied. The proposed ellipsoidal Helmholtz coil provides better performance in terms of field homogeneity, efficiency, and quality factor. The width of the lobe at 10% for the ellipsoidal coil is 20% bigger. Moreover, a significant improvement in the quality factor is observed in free space. Also, the efficiency is increased by 37%. Finally, the Signal to Noise Ratio (SNR) of the ellipsoidal coil is higher than that of the circular coil.

Section: Electrical Modelingmentioning

confidence: 99%

Design and Testing of a Radiofrequency Ellipsoidal Helmholtz Coil in Contrast with a Circular Pair for Nuclear Magnetic Resonance

Al-Snaie

2023

“…To calculate the electromagnetic field (B 1 ) produced by the proposed square and circular Helmholtz structures which consist of two symmetrical elements and have small dimensions compared to the wavelength, the superposition principle can be applied to obtain the total field as indicated in (2) and ( 5) for circular and square patterns [11][12][13]. The simulation code for the double square coil is programmed in MATLAB for a typical input data of I=1A, d=2.77cm, a=5cm, N=1, and µ 0 =4π×10 -7 mkgs -2 A -2 .…”

Section: Field Calculation and Pattern Plotmentioning

confidence: 99%

Design, Simulation, Modeling, and Implementation of a Square Helmholtz Coil in Contrast with a Circular Coil for MRI Applications

Ghaly

Khan

2019

This paper focuses on Helmholtz-type coils that can produce a second-order homogeneity field to be used for Magnetic Resonance Imaging (MRI) applications. A Helmholtz coil is a device used for producing a region of a nearly uniform magnetic field. It consists of two identical magnetic coils that are placed symmetrically along a common axis, one on either side of the experimental area, separated by a distance equal to the radius of the circular coil and half-length of the side of the square coils. Each coil carries an equal electrical current flowing in the same direction. The main objective of this article is to calculate the magnetic field provided by the coils at any point in space and to show and compare the uniform magnetic field induced by the square and circular Helmholtz coils. With the aid of MATLAB simulation tool, mathematical equations are simulated to demonstrate the axial magnetic field produced by one and two loops. Also, the design and simulation of electrical modeling for square and circular Helmholtz coils are performed using PSPICE. Finally, these coils are realized and tested experimentally, and the results for square and circular Helmholtz coils are compared.

“…The optimization of RF coils is the subject of continuous research. Currently, inductive coupling problems between radiating elements (conductors) are largely taken into account, and this task is partly facilitated for periodic structures [10][11][12]. For RF coils that do not have a specific periodicity, optimization and implementation are more challenging.…”

Section: Introductionmentioning

confidence: 99%

“…An improvement in the homogeneity of the field passes necessarily by the addition of coaxial turns. Thus, original structures, generally contained in a spherical and ellipsoidal envelope and having four or more free element loops have already been proposed [10][11][12] and very interesting properties in terms of homogeneity and sensitivity are obtained. A certain number of possibilities nevertheless remain to be analyzed.…”

Section: Introductionmentioning

confidence: 99%

Design and Modeling of a Radiofrequency Coil Derived from a Helmholtz Structure

Ghaly

Al-Snaie

Ali

2019

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.