Design of arbitrarily homogeneous permanent magnet systems for NMR and MRI: Theory and experimental developments of a simple portable magnet

Hugon, Cédric; d'Amico, F; Aubert, G.; Sakellariou, Dimitrios

doi:10.1016/j.jmr.2010.04.003

Cited by 50 publications

(60 citation statements)

References 24 publications

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“…(7.5 mm) was reserved for non-magnetic material. Exact numerical calculations were then performed using analytical formulae from the literature [11] to determine the maximum field strength obtainable in assemblies of two, four, eight and twenty-four of the block units surrounding the void (or ''bore"), assuming perfectly rigid and uniform magnetizations over the block volumes. Demagnetization within permanent magnet arrays can become an important factor when high magnetic fields are involved.…”

Section: Design Of Pseudo-halbach Arraysmentioning

confidence: 99%

“…The experimental data reproduce only roughly the theoretical predictions, even when advanced modeling including demagnetization was used. Since the magnetic pieces were not sorted beforehand in order to have controlled characteristics [11], significant variations in magnitude and direction of magnetization could be Fig. 2.…”

Section: Performance Of the Magnet Arraysmentioning

confidence: 99%

“…The cylindrical structure and later the spherical structure [5] allowed dipolar magnetic fields exceeding 2 T to be produced. Since then, several research groups and companies have refined Halbach's structures and together with shim coils magnets up to around 1.5 T can be obtained with homogeneity to better than 0.05 ppm, allowing for the resolution of chemical shifts and nuclear spinspin couplings in the measured NMR spectra [6][7][8][9][10][11][12][13][14]. The sensitivity at 1.5 T is around 10 À7 1 H moles, sufficing for most analyses of solution-state samples in the synthetic chemistry laboratory and at a price point that can enter the teaching laboratory.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Low-cost, pseudo-Halbach dipole magnets for NMR

Tayler

Sakellariou

2017

Journal of Magnetic Resonance

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a b s t r a c tWe present designs for compact, inexpensive and strong dipole permanent magnets aimed primarily at magnetic resonance applications where prepolarization and detection occur at different locations. Lowhomogeneity magnets with a 7.5 mm bore size and field up to nearly 2 T are constructed using low-cost starting materials, standard workshop tools and only few hours of labor -an achievable project for a student or postdoc with spare time. As an application example we show how our magnet was used to polarize the nuclear spins in approximately 1 mL of pure [13 C]-methanol prior to detection of its highresolution NMR spectrum at zero field (measurement field below 10 À10 T), where signals appear at multiples of the carbon-hydrogen spin-spin coupling frequency 1 J CH ¼ 140:7ð1Þ Hz.

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Section: Design Of Pseudo-halbach Arraysmentioning

confidence: 99%

Section: Performance Of the Magnet Arraysmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Low-cost, pseudo-Halbach dipole magnets for NMR

Tayler

Sakellariou

2017

Journal of Magnetic Resonance

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“…High homogeneity can be achieved by precisely positioning a number of shim pieces of permanent magnets. Different methodologies of passive shimming are being developed by a number of research and development groups, and there have been remarkable improvements in field homogeneity, especially in the fields of portable NMR/MRI with single-sided [11][12][13][14][15][16] and closed [17][18][19][20][21][22] 3 permanent magnets. The details including instrumentations and applications are reviewed elsewhere [23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children

Terada

Kono

Ishizawa

et al. 2013

Journal of Magnetic Resonance

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We adopted a combination of pieces of permanent magnets and a single-channel (SC) shim coil to shim the magnetic field in a magnetic resonance imaging system dedicated for skeletal age assessment of children. The target magnet was a 0.3-T open and compact permanent magnet tailored to the hand imaging of young children. The homogeneity of the magnetic field was first improved by shimming using pieces of permanent magnets. The residual local inhomogeneity was then compensated for by shimming using the SC shim coil. The effectiveness of the shimming was measured by imaging the left hands of human subjects and evaluating the image quality. The magnetic resonance images for the child subject clearly visualized anatomical structures of all bones necessary for skeletal age assessment, demonstrating the usefulness of combined shimming.

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“…Several groups have recently reported on such permanent magnets (see, for example, Ref. [2]); however, one design with outstanding performance deserves special attention: Danieli et al have designed and built a magnet smaller than a tea mug that can be shimmed mechanically and has a proton resonance frequency of 30 MHz. [3] The basic design follows that of the Halbach magnet but with additional adjustments for mechanical shimming (Figure 1).…”

mentioning

confidence: 99%

Towards Portable High‐Resolution NMR Spectroscopy

Luy

2010

Angew Chem Int Ed

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The sensitivity and resolution of modern high-resolution NMR spectrometers are closely interlinked with ever-higher magnetic field strengths. The recent installation of the first 1 GHz spectrometer in Lyon impressively demonstrates the effort and profound technological development made in this area. However, the majority of applications in classical chemistry do not need this kind of resolution. In contrast, the high costs and intensive maintenance of modern highresolution NMR spectrometers with superconducting magnets prevent the employment of NMR spectroscopy in chemical research and related fields, such as quality control and chemical engineering. There are also many applications where the sample cannot be moved to or into the spectrometer. As todays state-of-the-art high-resolution NMR spectrometers are extremely heavy and fragile with respect to their environmental conditions, the analysis in such cases cannot be performed. Thus, in light of these considerations, there is a strong application-driven need for small, relatively inexpensive, easy to maintain, and portable high-resolution NMR spectrometers.The first portable NMR spectrometer was developed in 1996 by the group of Blümich at the RWTH Aachen: the NMR-MOUSE was a giant breakthrough, with a small permanent magnet used for the polarization of nuclear spins, a heavy box containing the radio-frequency (RF) amplifiers, and a laptop for control.[1] This development was followed by a number of different tabletop NMR instruments, for example, several configurations were constructed by ACT/ Magritek, the Bruker Minispec series, the Oxford Instruments MQC, and clinically oriented systems from T2 Biosystems and nanoMR.However, all the systems that are readily available today are designed to measure the relative relaxation rates of bulk samples, and allow, for example, the acquisition of 3D images or the determination of the overall fat content of food products. The spectrometers with their small, unshimmed magnets generally do not allow the resolution of different chemical shifts, which means they are of no use for classical NMR spectroscopic applications. A number of fundamental issues concerning the design of the magnets and the electronics needed for spectrum acquisition have to be overcome to achieve a portable high-resolution NMR spectrometer.The three major concerns that have to be solved to obtain a useful portable high-resolution NMR spectrometer are: 1) the design of a magnet with sufficient homogeneity for the acquisition of spectra with chemical-shift resolution, 2) the stabilization of the magnet under real-life conditions, 3) the development of acquisition techniques that allow the use of lightweight electronics.Recently, considerable progress has been made in all three areas, thus opening up the possibility of portable highresolution NMR spectrometers within the next decade.The most crucial factor for portable NMR spectroscopy is the design of a small magnet with sufficient homogeneity to allow sub-ppm resolution of the chemical shift. As heliumc...

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Design of arbitrarily homogeneous permanent magnet systems for NMR and MRI: Theory and experimental developments of a simple portable magnet

Cited by 50 publications

References 24 publications

Low-cost, pseudo-Halbach dipole magnets for NMR

Low-cost, pseudo-Halbach dipole magnets for NMR

Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children

Towards Portable High‐Resolution NMR Spectroscopy

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