A high-field air-cored magnet coil design for fast-field-cycling NMR

Schweikert, K. H.; Krieg, R.; Noack, F.

doi:10.1016/0022-2364(88)90158-8

Cited by 38 publications

(32 citation statements)

References 11 publications

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“…The low-inductance air core magnets used for FFC are generally optimized for short switching times and minimal power consumption rather than for high field homogeneity (Schweikert et al, 1988). For water NMRD studies, an inhomogeneity of 200 ppm (in a 10-mm sample), as for our instrument, does not lead to significant signal loss during the ca.…”

Section: The Ffc Spectrometermentioning

confidence: 98%

Multinuclear Relaxation Dispersion Studies of Protein Hydration

Halle

Денисов

Venu

Biological Magnetic Resonance

270

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Section: The Ffc Spectrometermentioning

confidence: 98%

Multinuclear Relaxation Dispersion Studies of Protein Hydration

Halle

Денисов

Venu

Biological Magnetic Resonance

270

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“…More improvements were made by Compton (45) who developed a distributed-arc coil design giving gradients departing from the desired characteristics by a predetermined error. Schweikert et al (46) calculated optimized currents at specific surface elements, and Wong et al (47) proposed an approach in which the current and the number of turns are kept fixed, while the current element position is allowed to vary. A benefit of this type of coil design method is that there is no stage of approximation between a calculated continuous current density and the practical realization of discrete current carrying wires.…”

Section: Coils With Distributed Windingsmentioning

confidence: 99%

Theory of gradient coil design methods for magnetic resonance imaging

Hidalgo-Tobón

2010

Concepts Magnetic Resonance

133

104

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The process to produce an MR image includes nuclear alignment, RF excitation, spatial encoding, and image formation. In simple terms, an magnetic resonance imaging (MRI) system consists of five major components: a magnet, gradient systems, an RF coil system, a receiver, and a computer system. To form an image, it is necessary to perform spatial localization of the MR signals, which is achieved using gradient coils. In modern MRI, gradient coils able to generate high gradient strengths and slew rates are required to produce high imaging speeds and improved image quality. MRI also requires the use of gradient coils that generate magnetic fields, which vary linearly with position over the imaging volume. Gradient coils for MRI must therefore have high current efficiency (defined as the ratio of gradient generated to current drawn), short switching time (i.e., low inductance), gradient linearity over a large volume, low power consumption, and minimal interaction with any other equipment, which would otherwise result in eddy currents. Over the last two decades new methods of gradient coil design have been developed, and a combination of these methods can be a mixture of them trying to avoid discomforts to patients that at the end is the center of all the technological efforts in the art of MRI.

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“…In any case, where field-cycling studies are available, the characteristic effects of collective molecular motions on the relax ation process have been detected only on a much slower frequency scale, namely at Larmor frequencies in the kilohertz regime! Hence, to allow a more reli able analysis of the dynamics in reentrant systems, we have extended Dong's work on 6OCB-8OCB mix tures to significantly lower frequencies using the field-cycling apparatus developed in our laboratory [23][24][25]. To a large extent it eliminates the sensitivity problems of standard NMR in weak Zeeman fields [16,17].…”

Section: The Problemmentioning

confidence: 99%

Proton Spin Relaxation in Reentrant Nematic Cyano -biphenyl Liquid Crystals

Schweikert

Noack

1989

Zeitschrift Für Naturforschung A

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The frequency dependence of the longitudinal proton spin relaxation time Tx was measured by field-cycling and standard NMR techniques in the nematic, smectic and reentrant nematic mesophases of the reentrant liquid crystal 6OCB-8OCB. The results clearly demonstrate that, in contrast to conclusions reported in the literature, the underlying relaxation mechanisms are the same for the nematic and reentrant nematic order, but different in the nematic and smectic phase. In particular, at low frequencies the nematic and reentrant samples reveal a square-root dispersion profile (T, ~ v1 2) characteristic for nematic director fluctuations, whereas the smectic samples show a dissimilar and only very narrow dispersion step. It can be attributed to a linear relaxation time increase (Tx ~ v1) expected for smectic-type order fluctuations. The experimental data are described and discussed in terms of four molecular processes, namely nematic or smectic order fluctuations, self-diffusion, rotational motions, and a resonant proton nitrogen coupling.

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A high-field air-cored magnet coil design for fast-field-cycling NMR

Cited by 38 publications

References 11 publications

Multinuclear Relaxation Dispersion Studies of Protein Hydration

Multinuclear Relaxation Dispersion Studies of Protein Hydration

Theory of gradient coil design methods for magnetic resonance imaging

Proton Spin Relaxation in Reentrant Nematic Cyano -biphenyl Liquid Crystals

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