A Finite Difference Method for the Design of Gradient Coils in MRI—An Initial Framework

Zhu, Mingjian; Xia, Ling; F, Liu; Zhu, Jianfeng; Kang, Liyi; Crozier, Stuart

doi:10.1109/tbme.2012.2188290

Cited by 36 publications

(35 citation statements)

References 35 publications

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“…And other one is continuous current densityspace methods which is more effective. Compared with traditional design methods such as target field method, the greatest advantage of IBEM lies in its flexibility and efficiency for arbitrary shaped structures [5].…”

Section: Introductionmentioning

confidence: 99%

IBEM applied to the design of gradient coils for superconducting MRI

Yan

et al. 2015

2015 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices (ASEMD)

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This paper proposes an efficient design method for designing MRI gradient coils on a cylindrical surface geometry, using an inverse boundary element method (IBEM). Based on the approximate current density over the whole coils space, the magnetic field distribution can be obtained in the discrete form. An objective function is found to evaluate the minimum error between actual magnetic field that coils generate and desired magnetic field. Finally, the current distribution is transformed to the winding pattern of gradients via the relationship between current and stream function. This method can be used for coils on arbitrary surface shapes. The design examples of x-gradient coil, z-gradient are shown to demonstrate such method is more efficient and versatile to apply to the design of coils. Such method can also be used to design shim coils.

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Section: Introductionmentioning

confidence: 99%

IBEM applied to the design of gradient coils for superconducting MRI

Yan

et al. 2015

2015 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices (ASEMD)

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“…One of the frequently used methods to 250 B. Garda and Z. Galias give preference to a particular solution with desirable properties is the Tikhonov regularization method (Sikora et al, 1980;Zhu et al, 2012). This method of solving LSQ problems is widely used when the linear system of equations is ill-conditioned.…”

Section: Introductionmentioning

confidence: 99%

Tikhonov regularization and constrained quadratic programming for magnetic coil design problems

Garda

Galias

2014

International Journal of Applied Mathematics and Computer Science

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In this work, the problem of coil design is studied. It is assumed that the structure of the coil is known (i.e., the positions of simple circular coils are fixed) and the problem is to find current distribution to obtain the required magnetic field in a given region. The unconstrained version of the problem (arbitrary currents are allowed) can be formulated as a Least-SQuares (LSQ) problem. However, the results obtained by solving the LSQ problem are usually useless from the application point of view. Moreover, for higher dimensions the problem is ill-conditioned. To overcome these difficulties, a regularization term is sometimes added to the cost function, in order to make the solution smoother. The regularization technique, however, produces suboptimal solutions. In this work, we propose to solve the problem under study using the constrained Quadratic Programming (QP) method. The methods are compared in terms of the quality of the magnetic field obtained, and the power of the designed coil. Several 1D and 2D examples are considered. It is shown that for the same value of the maximum current the QP method provides solutions with a higher quality magnetic field than the regularization method.

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“…In practice, the continuous-current density-based method is usually combined with other numerical algorithms such as the boundary element method (BEM) [6,[31][32][33] or the finite difference method (FDM) [34][35][36]. These numerical methods produce continuous current density profiles that can be used to obtain a coil-winding pattern with the aid of a stream function.…”

Section: Gradient Coil Design Methodsmentioning

confidence: 99%

“…The target field approach is commonly used for gradient coil design [20] and this method was formulated in a finite-difference framework in this thesis [34] and is briefly summarized here. For cylindrical gradient coils, based on the Bio-Savart law, the z component of the magnetic flux density can be derived as [34] z , , Generally, there are requirements to control one or more coil performance parameters during the gradient coil design, for example, power dissipation, magnetic energy etc.…”

Section: Finite Difference Methods For Gradient Coil Designmentioning

confidence: 99%

“…For cylindrical gradient coils, based on the Bio-Savart law, the z component of the magnetic flux density can be derived as [34] z , , Generally, there are requirements to control one or more coil performance parameters during the gradient coil design, for example, power dissipation, magnetic energy etc.…”

Section: Finite Difference Methods For Gradient Coil Designmentioning

confidence: 99%

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Gradient coil design and acoustic noise control in magnetic resonance imaging systems

Wang¹

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In magnetic resonance imaging (MRI), three-dimensional linearly varied magnetic field gradients are required in the imaging volume, for the encoding of the spatial information of the imaged object.The gradient magnetic field is generated by gradient coils, whose performance directly affects the final MR image quality. Modern MRI applications demand gradient coils to be designed with higher performance such as a faster slew rate for rapid imaging, and fewer system interactions to ensure distortion-free images.During MR imaging, the gradient coil current switches quickly and the alternating current under a strong magnetic field generates a large Lorentz force, thus increasing the vibrations and noise in the gradient assembly, and the vibrations can also transmit to other components in the system. Moreover, the gradient magnetic field induces eddy currents on the surrounding conductive materials, resulting in further mechanical vibration. The sound pressure level (SPL) of an MRI scanner very commonly exceeds 100 dB, which may be discomforting to patients. Therefore, an effective acoustic noise control is necessary for the MRI operation.This thesis attempts to design a novel gradient coil system in an MRI scanner with a particular focus on the investigation of an acoustic noise control scheme. A brief summary of the thesis work is as follows.(1) Gradient coil design A conventional cylindrical MRI scanner has a long patient bore, which may make some patients uneasy due to claustrophobia. In order to alleviate this, an asymmetric gradient coil was proposed to accommodate an asymmetric MRI magnet. The coil was designed with a number of features, for example, to enable the installation of the shim tray, the coil was configured with one end connected and the other end separated. The electromagnetic and acoustic performances were also improved compared with a conventional non-connected coil system.The stream function approach is commonly used in gradient coil design, but an issue with this design is a connection problem between coil loops. To eliminate the field errors due to the coil connections, this thesis proposed a novel spiral coil design scheme, including both transverse coils and a longitudinal coil. The proposed coil design method was not only able to improve the magnetic II performance of the coil, but also could integrate the cooling system into the coil design using hollow wires in the discrete wire space.Wire spacing is a major engineering problem in gradient coil design. Conventional gradient coils are designed with three primary layers and three shielding layers, and in general, primary transverse coils are located in two layers separated by a very dense wire structure. In this thesis, a novel gradient coil design strategy using a layer-sharing scheme was proposed. This design scheme mutually combined the x and y gradient coil layers, effectively utilizing the unoccupied or sparse coil-layer space. The new method was modelled in the case of an asymmetric head coil design, and enhanced coil performan...

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A Finite Difference Method for the Design of Gradient Coils in MRI—An Initial Framework

Cited by 36 publications

References 35 publications

IBEM applied to the design of gradient coils for superconducting MRI

IBEM applied to the design of gradient coils for superconducting MRI

Tikhonov regularization and constrained quadratic programming for magnetic coil design problems

Gradient coil design and acoustic noise control in magnetic resonance imaging systems

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