Chapter 3. New Trends in Field-cycling NMR Technology

Anoardo, Esteban; Kruber, Stephan; Forte, Guillermo Omar; Dominguez, Gabriela

doi:10.1039/9781788012966-00067

Cited by 3 publications

(4 citation statements)

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“…Both the magnetic field transients after switching and the thermomechanical stress of the magnet increase at higher slew-rates. While an adequate current control strategy can mitigate transient instabilities in a short time, magnetic field shifts due to thermomechanical deformations of the magnet cannot be compensated (the magnetic field must be controlled instead) [36]. That is, in a system operating with a current control system (like our case), the temporal compression of the magnetic field pulse sequence may turn the magnetic field instable due to geometry variations of the magnet under thermal stress.…”

Section: Discussionmentioning

confidence: 99%

Fast iron oxide-induced low-field magnetic resonance imaging

Rodriguez¹,

Erro²,

Anoardo³

2020

J. Phys. D: Appl. Phys.

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Dynamic images acquired by proton fast field-cycling magnetic resonance imaging are presented for the first time. Image contrast mediated by superparamagnetic iron oxide nanoparticles and weighted by the spin-lattice (T1) relaxation time, and both spin-lattice and spin-spin (T2) relaxation times, are discussed. Image acquisition and processing within 8 s is allowed for real-time recording of exemplary physical situations evolving in a compatible time-scale. Two simple examples are shown with the corresponding videos assembled by sequencing the acquired images. Fast iron oxide-induced low-field magnetic resonance imaging (MRI) constitutes the first step in the development of field-cycling functional MRI for biomedical and physical applications.

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Section: Discussionmentioning

confidence: 99%

Fast iron oxide-induced low-field magnetic resonance imaging

Rodriguez¹,

Erro²,

Anoardo³

2020

J. Phys. D: Appl. Phys.

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“…The design of new FFC-NMR power supplies for non-academic applications has been a continuous challenge [8,20,32,33]. Among the most important aspects are the volume size of the whole equipment, the electric power for operation and the cooling requirements.…”

Section: Discussionmentioning

confidence: 99%

“…Electrical resistance: R M = 3 Ω; • Self-inductance: L M = 270 mH; • Magnetic flux density/magnet current ratio: B i M = 0.05 T/A; • Maximum magnet current: i M_max = 5 A. The use of this magnet in FFC-NMR requires a power supply design with the following specifications [20][21][22]:…”

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confidence: 99%

FFC-NMR Power Supply with Hybrid Control of the Semiconductor Devices

Roque,

Sousa,

Sebastião

et al. 2023

JLPEA

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The performance of FFC-NMR power supplies is evaluated not only considering the technique requirements but also comparing efficiencies and power consumption. Since the characteristics of FFC-NMR power supplies depend on the power circuit topology and on the control solutions, the control design is a core aspect for the development of new FFC systems. A new hybrid solution is described that allows controlling the power of semiconductors by switches (ON/OFF mode) or as a linear device. The approach avoids over-design of the power supply and makes it possible to implement new low power solutions constituting a novel design by joining a continuous match between the ON/OFF mode and the linear control of the power semiconductor devices.

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“…Field-cycling nuclear magnetic resonance (NMR) experiments may demand rapid variations between different magnetic field intensities, so electromagnets are usually involved. Technological developments on this NMR sub-field are oriented towards working at lower magnetic fields, with higher requirements on the magnetic field homogeneity and stability, improving magnet switching performance and boosting the SNR [15]. Experiments may be achieved by polarizing the spin system in a high intensity magnetic field, then quickly switching down to a low intensity field for a preestablished evolution period, and finally bringing the field intensity back to a higher value for acquisition (magnetic field cycling sequence referred to as "pre-polarized" or PP).…”

Section: Introductionmentioning

confidence: 99%

A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals

Romero

Rodriguez

Anoardo

2020

Journal of Magnetic Resonance

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We present a fast field-cycling NMR relaxometer with added magnetic resonance imaging capabilities. The instrument operates at a maximum proton Larmor frequency of 5 MHz for a sample volume of 35 mL. The magnetic field homogeneity across the sample is 1400 ppm. The main field is generated with a notch-coil electromagnet of own design, fed with a current whose stability is 220 ppm. We show that images of reasonable quality can still be produced under such conditions. The machine is being designed for concept testing of the involved instrumentation and specific contrast agents aimed for field-cycling magnetic resonance imaging applications. The general performance of the prototype was tested through localized relaxometry experiments, T 1 -dispersion weighted images, temperature maps and T 1 -weighted images at different magnetic field intensities. We introduce the concept of positive and negative contrast depending on the use of pre-polarized or nonpolarized sequences. The system is being improved for pre-clinical studies in small animals.

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Chapter 3. New Trends in Field-cycling NMR Technology

Cited by 3 publications

References 0 publications

Fast iron oxide-induced low-field magnetic resonance imaging

Fast iron oxide-induced low-field magnetic resonance imaging

FFC-NMR Power Supply with Hybrid Control of the Semiconductor Devices

A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals

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