An optimized target-field method for MRI transverse biplanar gradient coil design

Zhang, Rui; Xu, Jing; Fu, Youyi; Li, Yangjing; Huang, Kefu; Zhang, Jue; Fang, Jing

doi:10.1088/0957-0233/22/12/125505

Cited by 22 publications

(11 citation statements)

References 17 publications

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“…), referred to as bi‐planar gradient coils, which are attached to the two opposing magnetic poles: this configuration maximizes the open space in the magnet gap. There have been many publications outlining advances in the design of such bi‐planar gradients …”

Section: Advances In Hardwarementioning

confidence: 99%

“…There have been many publications outlining advances in the design of such bi-planar gradients. [27][28][29] In terms of gradient performance, typical numbers for modern-day gradients on the "whole body" low-field MRI systems are inductances on the order of 300-500 μH, resistances of 3-4 Ω, and efficiencies of 4-8 mT/m/A. Maximum gradient strengths for water-cooled gradient coils are on the order of 25 mT/m with a slew rate of 50 T/m/s.…”

Section: Gradient Designmentioning

confidence: 99%

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Low‐field MRI: An MR physics perspective

Marques

Simonis

Webb

2019

Magnetic Resonance Imaging

246

266

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Historically, clinical MRI started with main magnetic field strengths in the ∼0.05–0.35T range. In the past 40 years there have been considerable developments in MRI hardware, with one of the primary ones being the trend to higher magnetic fields. While resulting in large improvements in data quality and diagnostic value, such developments have meant that conventional systems at 1.5 and 3T remain relatively expensive pieces of medical imaging equipment, and are out of the financial reach for much of the world. In this review we describe the current state‐of‐the‐art of low‐field systems (defined as 0.25–1T), both with respect to its low cost, low foot‐print, and subject accessibility. Furthermore, we discuss how low field could potentially benefit from many of the developments that have occurred in higher‐field MRI. In the first section, the signal‐to‐noise ratio (SNR) dependence on the static magnetic field and its impact on the achievable contrast, resolution, and acquisition times are discussed from a theoretical perspective. In the second section, developments in hardware (eg, magnet, gradient, and RF coils) used both in experimental low‐field scanners and also those that are currently in the market are reviewed. In the final section the potential roles of new acquisition readouts, motion tracking, and image reconstruction strategies, currently being developed primarily at higher fields, are presented. Level of Evidence : 5 Technical Efficacy Stage : 1 J. Magn. Reson. Imaging 2019.

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Section: Advances In Hardwarementioning

confidence: 99%

Section: Gradient Designmentioning

confidence: 99%

Low‐field MRI: An MR physics perspective

Marques

Simonis

Webb

2019

Magnetic Resonance Imaging

246

266

View full text Add to dashboard Cite

show abstract

“…The stored energy is calculated with magnetic potential vector A ( r ) and current density vector J ( r ), hence in the gradient coil system, the total stored energy could be written as

W = \int \underset{s}{false\int} \int \underset{s^{'}}{false\int} J false(r false) A false(r, D_{a} false) + J false(r false) A false(r^{'}, D_{b} false) + J false(r^{'} false) A false(r^{'}, D_{b} false) d r d r^{'}

where the first and third items result from self‐inductance of gradient coils and MC coil, while the second is mutual inductance between them.…”

Section: Coil Optimizationmentioning

confidence: 99%

Pole plate effected gradient coils design in permanent magnet MRI system

Lopez

Chen

et al. 2016

Concepts Magn Reson

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Pole plate in permanent magnet MRI system leads to serious impact on the strength, linearity, and inductance of gradient coils due to the induced current of its pure iron material. In this article, a modified mirror current (MC) model of pole plate based on z gradient coil is established, aiming at improving gradient coil performance. Levenberg‐Marquardt (LM) algorithm is applied for the gradient coil optimization with and without constraint of the current density coefficient that determines the coil complexity and structure. With the optimal constraint radius 4.466 and 4.942, the minimum square of gradient field errors are obtained as 3.1991×10−12 and 3.5711×10−6 for longitudinal and transverse gradient coils, respectively. Optimization results combining linearity, inductance and field error ameliorate all three parameters prominently comparing with the original MC model, which proves the efficiency of the modified MC model and LM optimization algorithm in gradient coil construction to compensate the pole plate effect.

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“…To address the difficulties that are encountered in a lowresource setting, new MR systems are being proposed such as MR scanners based on resistive magnets [5], [6] or systems that utilize a Halbach permanent magnet array [7], [8]. For a resistive magnet, gradient coil design runs along similar lines as for conventional MRI systems, albeit typically for smaller bore sizes and lower power requirements.…”

Section: Introductionmentioning

confidence: 99%

Gradient Coil Design and Realization for a Halbach-Based MRI System

et al. 2020

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In this paper we design and construct gradient coils for a Halbach permanent magnet array magnetic resonance (MR) scanner. The target field method, which is widely applied for the case of axial static magnetic fields, has been developed for a transverse static magnetic field as produced by a Halbach permanent magnet array. Using this method, current densities for three gradient directions are obtained and subsequently verified using a commercial magneto-static solver. Stream functions are used to turn the surface current densities into wire patterns for constructing the gradient coils. The measured fields are in good agreement with simulations and their prescribed target fields. Three dimensional images have been acquired using the constructed gradient coils with very low degree of geometric distortion.

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An optimized target-field method for MRI transverse biplanar gradient coil design

Cited by 22 publications

References 17 publications

Low‐field MRI: An MR physics perspective

Low‐field MRI: An MR physics perspective

Pole plate effected gradient coils design in permanent magnet MRI system

Gradient Coil Design and Realization for a Halbach-Based MRI System

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