A 4 tesla/1 meter superferric MRI magnet

Schmidt, W.; Huson, F. R.; MacKay, W. W.; Rocha, R.

doi:10.1109/20.133511

Cited by 11 publications

(13 citation statements)

References 4 publications

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“…In general, the numerical solution of Eq. [7] is a difficult task, because the problem is formulated from a Fredhom integral equation of the first kind. This belongs to the class of so-called ill-posed problems.…”

Section: Mathematical Modelmentioning

confidence: 99%

Current density mapping approach for design of clinical magnetic resonance imaging magnets

Crozier

Zhao

Doddrell

2002

Concepts Magn. Reson.

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Novel current density mapping (CDM) schemes are developed for the design of new actively shielded, clinical magnetic resonance imaging (MRI) magnets. This is an extended inverse method in which the entire potential solution space for the superconductors has been considered, rather than single current density layers. The solution provides an insight into the required superconducting coil pattern for a desired magnet configuration. This information is then used as an initial set of parameters for the magnet structure, and a previously developed hybrid numerical optimization technique is used to obtain the final geometry of the magnet. The CDM scheme is applied to the design of compact symmetric, asymmetric, and open architecture 1.0 -1.5 T MRI magnet systems of novel geometry and utility. A new symmetric 1.0-T system that is just 1 m in length with a full 50-cm diameter of the active, or sensitive, volume (DSV) is detailed, as well as an asymmetric system in which a 50-cm DSV begins just 14 cm from the end of the coil structure. Finally a 1.0-T open magnet system with a full 50-cm DSV is presented. These new designs provide clinically useful homogeneous regions and have appropriately restricted stray fields but, in some of the designs, the DSV is much closer to the end of the magnet system than in conventional designs. These new designs have the potential to reduce patient claustrophobia and improve physician access to patients undergoing scans. KEY WORDS: magnetic resonance imaging magnet; symmetric design; asymmetric design; open magnet design; current density mapping method

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Section: Mathematical Modelmentioning

confidence: 99%

Current density mapping approach for design of clinical magnetic resonance imaging magnets

Crozier

Zhao

Doddrell

2002

Concepts Magn. Reson.

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“…Conventional medical MRI systems are typically around 1.6 -2.0 m in length with free bore diameters in the range 0.8 -1.0 m (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The errors are usually less than 10 ppm rms over a 45-50 cm dsv.…”

mentioning

confidence: 99%

Asymmetric MRI Magnet Design Using a Hybrid Numerical Method

Zhao

Crozier

Doddrell

1999

Journal of Magnetic Resonance

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“…We have the following relations from: 6 ðn À mÞsin a P m n ðcos aÞ À cos a P mþ1 n ðcos aÞ ¼ ÀP mþ1 nÀ1 ðcos aÞ (B10)…”

mentioning

confidence: 99%

“…The spherical harmonic coefficients of one-turn circular coil, such as z2 and z4 shim coils, were given by many papers. 4,5 Some papers [6][7][8] gave the expression of the spherical harmonic coefficients to the cylindrical coil with volume, such as a solenoid coil.…”

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confidence: 99%

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Formulation of the spherical harmonic coefficients of the entire magnetic field components generated by magnetic moment and current for shimming

Noguchi

2014

Journal of Applied Physics

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For MRI and NMR magnet design, a highly homogeneous and high magnetic field has to be achieved by active and/or passive shimming. The active and passive shimming commonly homogenize the magnetic field around the magnet center by cancellation of the higher terms of a spherical harmonic series than the 0th term. So far, the spherical harmonic expression in the cylindrical coordinate system is well known for a circular coil, a solenoid coil, and magnetization of ferromagnetic material with/without its volume. In a shimming design, only the z-component of an inhomogeneous magnetic field is compensated because it is dominant to the performance of MRI/NMR. However, various kinds of MRI and NMR systems have recently been developed, and these magnets sometimes have an axially asymmetric configuration or generate a tilted magnetic field. Therefore, the entire x-, y-, and z-components have to be homogenized for such magnets. I derive the spherical harmonic expression of the entire components of magnetic field generated by a circular coil, a dipole coil, and a straight line current. In addition, since the entire magnetization components of the ferromagnetic material having the volume contribute the entire components of the magnetic field around the magnet center, I also derive the equations of the spherical harmonic coefficients of the magnetic field generated by ferromagnetic material. Since these equations need a numerical integration, such as the Gauss quadrature integration, the computation accuracy of the spherical harmonic coefficients is investigated against the number of the evaluation points. We can calculate the highly accurate spherical harmonic coefficients with the small number of the evaluation points. (C) 2014 AIP Publishing LLC

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A 4 tesla/1 meter superferric MRI magnet

Abstract: Superfenic technology was first applied to Magnetic Resonance Imaging (MRI magnets by the Texas Accelerator Center cm magnet. In a evolutionary step, this technology is now being applied to the development of a whole body 4 Tesla / 1 meter magnet. The design of such a magnet is presented.

Cited by 11 publications

References 4 publications

Current density mapping approach for design of clinical magnetic resonance imaging magnets

Current density mapping approach for design of clinical magnetic resonance imaging magnets

Asymmetric MRI Magnet Design Using a Hybrid Numerical Method

Formulation of the spherical harmonic coefficients of the entire magnetic field components generated by magnetic moment and current for shimming

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