Simulation and Optimization of a Permanent Magnet for Small-Sized MRI by Genetic Algorithm

2013 ◽  
Vol 341-342 ◽  
pp. 577-580
Author(s):  
Yi Yuan Cheng ◽  
Ling Xia ◽  
Wei He
Keyword(s):  
Magnetic Field ◽  
Permanent Magnet ◽  
Homogeneous Magnetic Field ◽  
Main Magnetic Field ◽  
Resonance Imaging ◽  
Simulation And Optimization ◽  
Field Uniformity ◽  
Main Magnet ◽  
Magnetic Resonance Imaging Mri ◽  
The Magnetic Field

The main magnet produces the main magnetic field in the imaging area as one of the important parts of the magnetic resonance imaging (MRI) system. In a permanent MRI magnet, the widespread end effect causes a non-uniform magnetic field distribution and affects the imaging quality. In this paper, an H-type permanent magnet for small-sized MRI applications was designed; in particular, we added an optimized shimming ring outside the pole piece to improve the magnetic field uniformity. Genetic algorithms are used to solve the complex and nonlinear calculation of the magnetic field. The simulation results show that the magnet optimized by the proposed method generates a homogeneous magnetic field that can be easily implemented in practice.

A trail of artificial vestibular stimulation: electricity, heat, and magnet

2012 ◽  
Vol 108 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Aasef G. Shaikh
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
Semicircular Canals ◽  
Vestibular Stimulation ◽  
Clinical Neurology ◽  
Ion Currents ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
The Magnetic Field

The interaction between the magnetic field of a magnetic resonance imaging (MRI) machine and ion currents within the inner-ear endolymph results in a Lorentz force. This force produces a pressure that pushes on the cupula within the semicircular canals causing nystagmus and vertigo. Here I discuss several implications of this unique and noninvasive way to stimulate the vestibular system in experimental neurophysiology and clinical neurology.

Simulation and Optimization of an Octagonal Halbach Permanent Magnet Array for Small-Size NMR

2014 ◽  
Vol 543-547 ◽  
pp. 509-513 ◽  
Author(s):  
Qiao Yan Chen ◽  
Guang Cai Zhang ◽  
Ya Jie Xu ◽  
Yan Chang ◽  
Hui Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Permanent Magnet ◽  
Magnetic Field Strength ◽  
Small Volume ◽  
Simulation And Optimization ◽  
Magnetic Field Homogeneity ◽  
Field Homogeneity ◽  
Design And Manufacture ◽  
The Magnetic Field

Halbach magnet array has advantages of its small size and yokeless, so it has been widely used in various areas. In this paper, two Halbach permanent magnet arrays for small-size NMR with cube and octagonal shape, respectively, were compared in parameters of average magnetic field strength, field homogeneity and volume with the same material consumption. It was found that the octagonal shape magnet has better performance than the cube one. Then the field homogeneity optimization for octagonal magnet was performed. By analysis of magnetic field strength, the best homogeneity in 5mm DSV (Diameter of Spherical Volume) with 133.4ppm was achieved when the height of magnetic blocks is 16.25mm. After optimization, the magnetic field homogeneity has been significantly improved when the shape of magnet has small volume. This result laid a foundation for the design and manufacture of the octagonal Halbach permanent magnet array in small size.

scholarly journals The magnetic field homogeneity of coils by means of the space harmonics suppression of the current density distribution

2016 ◽  
Vol 5 (2) ◽  
pp. 401-408 ◽  
Author(s):  
Christophe Coillot ◽  
Eric Nativel ◽  
Michel Zanca ◽  
Christophe Goze-Bac
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Current Density Distribution ◽  
Homogeneous Magnetic Field ◽  
Modern World ◽  
Resonance Spectroscopy ◽  
Fourier Decomposition ◽  
Magnetic Field Homogeneity ◽  
Magnetic Resonance Imaging Mri ◽  
The Magnetic Field

Abstract. Electromagnetic coils are ubiquitously used in the modern world in motors, antennas, etc. In many applications (magnetic field coil calibration and nuclear magnetic resonance spectroscopy and imaging) there is a strong need for a homogeneous magnetic field. In this paper, we propose a simple modelling based on serial Fourier decomposition allowing the determination of the electrical conductor distribution to make the magnetic field homogeneous. The method is valid both for plane and axisymmetric geometries. The method allows the retrieval of the classical configurations of saddle coil for the plane geometry and Helmholtz coil for the axisymmetric one. The method is generalized for any number of electrical conductors and brings the perspective of new homogeneous magnetic resonance imaging (MRI) coil configuration.

scholarly journals Magnetic Field Simulation of Golay Coil

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Rashdi Shah Ahmad ◽  
Amiruddin Shaari ◽  
Chew Teong Han
Keyword(s):  
Magnetic Field ◽  
Gradient Coil ◽  
Main Magnetic Field ◽  
Signal Acquisition ◽  
Gradient Coils ◽  
Calculation Algorithm ◽  
Magnetic Field Simulation ◽  
Transverse Gradient ◽  
Magnetic Resonance Imaging Mri ◽  
The Magnetic Field

In the field of magnetic resonance imaging (MRI), besides the main magnetic field and the radio frequency (RF) system, the gradient coils system also plays an important role in signal acquisition. Generally, there are 2 transverse gradient coils and 1 longitudinal gradient coil. In this research, the magnetic field (or gradient) generated by the conventional transverse coil, namely the Golay coil was mapped. The calculation algorithm of the magnetic field generated was written in C-programming language, compiled by the GNU-compiler collection (GCC) and was based on a forward analytical approach by using the Biot-Savart Law. The data was then visualized by Gnuplot. The magnetic field was successfully calculated and plotted using open-source softwares running under Ubuntu operating system and will provide valuable data especially for gradient coil designer.

Improved Configuration of Halbach Magnets with a Homogeneous Magnetic Field for Portable NMR Device

2021 ◽  
Vol 36 (5) ◽  
pp. 548-558
Author(s):  
Yi-Yuan Cheng ◽  
Ming-Yang Su ◽  
Tao Hai ◽  
Ming Hui ◽  
Bao-lei Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fem Analysis ◽  
Pso Algorithm ◽  
Homogeneous Magnetic Field ◽  
Swarm Optimization ◽  
Halbach Array ◽  
Field Uniformity ◽  
Portable Nmr ◽  
3D Finite Element Method ◽  
The Magnetic Field

Halbach array magnets are widely used in portable nuclear magnetic resonance (NMR) devices that the homogeneity of the magnetic field generated by the array affects the imaging quality. In this paper, we propose some improvements to the construction of the Halbach magnets to enhance magnetic field uniformity. Using a Halbach array model comprising 16 magnets, all the calculations are based on 3D finite element method (FEM) analysis and optimized using the particle swarm optimization (PSO) algorithm. Comparisons of the results are shown to support the observations that the optimized and improved constructions can generate a more homogeneous magnetic field.

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

scholarly journals Finite Element Analysis of Magnetic Field Exciter for Direct Testing of Magnetocaloric Materials’ Properties

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2792
Author(s):  
Wieslaw Lyskawinski ◽  
Wojciech Szelag ◽  
Cezary Jedryczka ◽  
Tomasz Tolinski
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Magnetic Circuit ◽  
Homogeneous Magnetic Field ◽  
Element Analysis ◽  
Mcm Testing ◽  
Testing Region ◽  
Magnetocaloric Materials ◽  
Field Excitation ◽  
The Magnetic Field

The paper presents research on magnetic field exciters dedicated to testing magnetocaloric materials (MCMs) as well as used in the design process of magnetic refrigeration systems. An important element of the proposed test stand is the system of magnetic field excitation. It should provide a homogeneous magnetic field with a controllable value of its intensity in the MCM testing region. Several concepts of a magnetic circuit when designing the field exciters have been proposed and evaluated. In the MCM testing region of the proposed exciters, the magnetic field is controlled by changing the structure of the magnetic circuit. A precise 3D field model of electromagnetic phenomena has been developed in the professional finite element method (FEM) package and used to design and analyze the exciters. The obtained results of the calculations of the magnetic field distribution in the working area were compared with the results of the measurements carried out on the exciter prototype. The conclusions resulting from the conducted research are presented and discussed.

MRI Susceptibility Artefacts Related to Scaphoid Screws: the Effect of Screw Type, Screw Orientation and Imaging Parameters

2002 ◽  
Vol 27 (2) ◽  
pp. 165-170 ◽  
Author(s):  
M. GANAPATHI ◽  
G. JOSEPH ◽  
R. SAVAGE ◽  
A. R. JONES ◽  
B. TIMMS ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Titanium Alloy ◽  
Magnetic Resonance ◽  
Main Magnetic Field ◽  
Resonance Imaging ◽  
Metal Implants ◽  
Imaging Parameters ◽  
Susceptibility Artefact

Metal implants produce susceptibility artefacts in magnetic resonance imaging. We have explored the effects of scaphoid screw characteristics and orientation on MR susceptibility artefact. Titanium alloy, smallness and longitudinal alignment with the z-axis of the main magnetic field reduce the size of the susceptibility artefact.

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