An Optimal Design of Coaxial Coils With Constraints on Inner and Outer Multipole Magnetic Fields

Kitamura, Masashi; Kakugawa, S.; Maki, Koichi

doi:10.1109/tasc.2004.830884

Cited by 11 publications

(3 citation statements)

References 4 publications

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“…Multi-coil design has been often used in the design of conventional magnets [56], and it is easily adapted to the present case. The method consists in solving the inverse problem solution posed by the decomposition of the magnet in a set of coils, and by the search of their optimal dimensions, positions, and currents that produce the desired field.…”

Section: An Optimized 2-d Designmentioning

confidence: 99%

Quest for an open MRI scanner

Bertora

Borceto

Viale

et al. 2014

Bio-Medical Materials and Engineering

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A study of the motor cortex during the programming, execution and mental representation of voluntary movement is of great relevance; its evaluation in conditions close to reality is necessary, given the close integration of the visuomotor, sensory feedback and proprioceptive systems, as of yet, a functional Magnetic Resonance Imaging (fMRI) scanner allowing a human subject to maintain erect stance, observe the surroundings and conserve limb freedom is still a dream. The need for high field suggests a solenoid magnet geometry that forces an unnatural posture that affects the results, particularly when the motor cortex is investigated. In contrast in a motor functional study, the scanner should allow the subject to sit or stand, with unobstructed sight and unimpeded movement. Two approaches are presented here to solve this problem. In the first approach, an increased field intensity in an open magnet is obtained lining the "back wall" of the cavity with a sheet of current: this boosts the field intensity at the cost of the introduction of a gradient, which has to be canceled by the introduction of an opposite gradient; The second approach is an adaptation of the "double doughnut" architecture, in which the cavity widens at the center to provide additional room for the subject. The detailed design of this kind of structure has proven the feasibility of the solution.

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Section: An Optimized 2-d Designmentioning

confidence: 99%

Quest for an open MRI scanner

Bertora

Borceto

Viale

et al. 2014

Bio-Medical Materials and Engineering

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“…This method has already been used to design superconducting magnets which generate a uniform central magnetic field [6]. The design procedure of matrix shim system, however, is more complicated than that of magnets generating uniform magnetic field.…”

Section: A Solenoid Coilsmentioning

confidence: 99%

Development of Shimming System for a Highly Sensitive NMR Spectrometer With a Superconducting Split Magnet

Maki

Wakuda

Tsuchiya

et al. 2008

IEEE Trans. Appl. Supercond.

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A highly sensitive NMR spectrometer with a superconducting split magnet and a solenoid-type probe coil is being developed. One of the most challenging tasks is to achieve high homogeneity of magnetic field in a measuring volume with this configuration, because inevitable structural asymmetry and limited production accuracy of the magnet cause larger inhomogeneity of magnetic field compared with a conventional solenoid-type NMR spectrometer. Numerical estimation revealed that field correction capability of conventional shim coils, i.e., superconducting solenoid and saddle coils placed outside main coils, is insufficient for the split NMR magnet. Therefore, we have designed and constructed superconducting shim coils with sufficiently high capability by adopting the following three novel ideas: (1) superconducting shim coils are placed not only outside main coils but also inside them in the vicinity of a measuring volume; (2) superconducting shim coils with "periodically wavy" shape are utilized to correct non-axial inhomogeneous magnetic field; (3) the current of each superconducting shim coil is independently controlled to correct plural modes of magnetic field simultaneously.

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“…In both regions the magnetic flux density satisfies Laplace's equation (1) Solutions in the inner region which are finite at the origin represented in the spherical polar coordinates and by expansion in series of associated Legendre functions and powers of are well known [6]: (2) where the expansion coefficients are the strengths of the harmonics. In the outer region, (1) can also be solved as finite at infinity [7]:…”

Section: Expansion Of Stray Fieldsmentioning

confidence: 99%

Shielding Stray Magnetic Fields of Open High Field MRI Magnets

Kakugawa

Hino

Komura

et al. 2004

IEEE Trans. Appl. Supercond.

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We have developed a new magnet for open high field (0.7 T) MRI systems. Since MRI systems are installed in hospital sites, it is important to reduce stray magnetic fields of the magnets. We studied passive, active and hybrid shielding methods and compared them. In order to study feasibility of active shielding, we considered higher order multipole stray fields. We present details of the calculation method and the results.Index Terms-Linear programming, magnetic resonance imaging (MRI), multipole stray field, optimization.

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An Optimal Design of Coaxial Coils With Constraints on Inner and Outer Multipole Magnetic Fields

Cited by 11 publications

References 4 publications

Quest for an open MRI scanner

Quest for an open MRI scanner

Development of Shimming System for a Highly Sensitive NMR Spectrometer With a Superconducting Split Magnet

Shielding Stray Magnetic Fields of Open High Field MRI Magnets

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