Study on Shimming Method for Open Permanent Magnet of Mri

Ren, Ziyan; Xie, Dexin; Li, and Huixiang

doi:10.2528/pierm08122406

Cited by 8 publications

(6 citation statements)

References 8 publications

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“…This technique generally uses a very high static magnetic field produced by permanent magnets [1][2][3][4]. It is well known that the magnetic field homogeneity of imaging region is the most important criterion for optimizing MRI structures [5,6]. On the other hand, the magnetic field must be the greatest [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field in Mri Yokeless Devices: Analytical Approach

Ravaud¹,

Lemarquand²

2009

PIER

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Abstract-This paper presents a three-dimensional analytical expressions for studying the static magnetic field produced by Magnetic Resonance Imaging structures. This medical imaging technique uses a very high and uniform magnetic field produced by ring permanent magnets with rotating polarizations. However, the manufacturing of such ring permanent magnets is difficult to realize. Consequently, such ring permanent magnets are replaced by assemblies of tile permanent magnets uniformly magnetized. Unfortunately, the magnetic field produced by these tile permanent magnets uniformly magnetized is both less important and less uniform than the one produced by an idealized ring permanent magnet. We propose in this paper to study the influence of the number of tile permanent magnets used on the magnetic field properties.

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Section: Introductionmentioning

confidence: 99%

Magnetic Field in Mri Yokeless Devices: Analytical Approach

Ravaud¹,

Lemarquand²

2009

PIER

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“…[16,17] Shimming is the most commonly employed technique to decrease field inhomogeneities of magnetic systems. For permanent magnets, two shimming methods are generally used: 1) passive shimming, which corrects the magnetic field by ferromagnetic materials placed in specific locations along the magnet [18][19][20] and 2) active shimming, which adopts electromagnets with specialized coils to generate correction fields. [21,22] Several optimized permanent magnetic designs that generate a homogeneous magnetic field have been reported.…”

Section: Introductionmentioning

confidence: 99%

Additive Manufacturing of Hard Magnetic Passive Shims to Increase Field Homogeneity of a Halbach Magnet

et al. 2023

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Obtaining a highly homogeneous magnetic field is desired for field‐controlled applications. For example, the resolution of magnetic analysis methods can be improved by generating a stronger and more homogeneous field over the region of interest (ROI). A set of 3D‐printed passive shims is fabricated using additive manufacturing to improve the magnetic field homogeneity of a Halbach magnet assembly. The feedstock is a custom acrylonitrile butadiene styrene (ABS)‐hard magnet composite filament filled with 60% wt. isotropic NdFeB. Additionally, a method for investigating the remanence is developed and validated. The result reveals a good agreement between the new method and existing measurement techniques for the remanence of permanent magnets. It is also shown that the additive manufacturing procedure has negligible effects on the magnetic properties. Performing a parametric study over a rectangular ROI, an optimized shim configuration is achieved. In the optimized and 3D‐printed configuration, the average norm of the magnetic flux density, Bnorm, is increased by 13% and, more importantly, a 43% increase in the magnetic uniformity is obtained. These results highlight the great potential of freeform manufacturing, namely, additive manufacturing, to tailor the properties of magnet structures.

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“…In general, two shimming methods exists to increase the magnetic field homogeneity of a permanent magnet. (i) Passive shimming corrects the magnetic field by ferromagnetic materials placed on specific locations along the magnet 1 – 3 . (ii) Active shimming uses electro magnets with specialized coils to generate a correction field 4 , 5 .…”

Section: Introductionmentioning

confidence: 99%

Additive Manufactured and Topology Optimized Passive Shimming Elements for Permanent Magnetic Systems

Huber

Goertler

Abert

et al. 2018

Sci Rep

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A method to create a highly homogeneous magnetic field by applying topology optimized, additively manufactured passive shimming elements is investigated. The topology optimization algorithm can calculate a suitable permanent and nonlinear soft magnetic design that fulfills the desired field properties. The permanent magnetic particles are bonded in a polyamide matrix and they are manufactured with a low-cost, end-user 3D printer. Stray field measurements and an inverse stray field simulation framework can determine printing and magnetization errors. The customized shimming elements are manufactured by a selective melting process which produces completely dense soft magnetic metal parts. The methodology is demonstrated on a simple example of two axial symmetric cylindrical magnets, which generates a high inhomogeneous magnetic field. In this case, the maximum magnetic field density is 25 mT and the the homogeneity can be increased by a factor of 35 or down to 6‰. Simulation and measurement results point out a good conformity. Additional topology optimizations of more than one shimming element layer show the opportunity to make the manufactured magnetic system even more homogeneous.

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Study on Shimming Method for Open Permanent Magnet of Mri

Cited by 8 publications

References 8 publications

Magnetic Field in Mri Yokeless Devices: Analytical Approach

Magnetic Field in Mri Yokeless Devices: Analytical Approach

Additive Manufacturing of Hard Magnetic Passive Shims to Increase Field Homogeneity of a Halbach Magnet

Additive Manufactured and Topology Optimized Passive Shimming Elements for Permanent Magnetic Systems

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