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Journal of Magnetic Resonance

G Varma, O M Girard, S Mchinda, V H Prevost, A K Grant, G Duhamel, D C Alsop
Intense off-resonant RF irradiation can lead to saturation of the macromolecular pool magnetization and enhance bound pool dipolar order responsible for the inhomogeneous magnetization transfer (ihMT) effect, but the intensity of RF power in human imaging studies is limited by safety constraints on RF heating. High RF intensities can still be achieved if applied in short pulses with low duty-cycle. Here we investigate the benefits of low duty-cycle irradiation for MT and ihMT studies with both theoretical and experimental methods...
August 31, 2018: Journal of Magnetic Resonance
Sajad Hosseinnezhadian, Roberta Frass-Kriegl, Sigrun Goluch-Roat, Michael Pichler, Jürgen Sieg, Martin Vít, Marie Poirier-Quinot, Luc Darrasse, Ewald Moser, Jean-Christophe Ginefri, Elmar Laistler
A flexible transceiver array based on transmission line resonators (TLRs) combining the advantages of coil arrays with the possibility of form-fitting targeting cardiac MRI at 7 T is presented. The design contains 12 elements which are fabricated on a flexible substrate with rigid PCBs attached on the center of each element to place the interface components, i.e. transmit/receive (T/R) switch, power splitter, pre-amplifier and capacitive tuning/matching circuitry. The mutual coupling between elements is cancelled using a decoupling ring-based technique...
August 31, 2018: Journal of Magnetic Resonance
Yao Luo, Jun Zhang, Lin Chen, Shuhui Cai, Congbo Cai
Single-shot spatiotemporally encoded (SPEN) ultrafast magnetic resonance imaging (MRI) is of great value to both scientific research and clinical application owing to its capability for delivering MR images with greater robustness to magnetic field inhomogeneity and chemical-shift displacement effects than conventional methods like EPI due to high effective phase-encoded bandwidth. Many SPEN MRI methods have been developed, among which multi-slice SPEN MRI arises as a promising supplement to ultrafast multi-slice sampling...
August 31, 2018: Journal of Magnetic Resonance
Karol Borkowski, Artur Tadeusz Krzyżak
The intensity of the diffusion weighted NMR signal is described by the Stejskal-Tanner equation, which was derived under the assumption that the gradients are uniform throughout the sample. Nevertheless, it has been demonstrated numerous times that this condition is not fulfilled in the cases of virtually any clinical or research MRI scanners. Therefore, technically, the Stejskal-Tanner equation is valid only for a very specific case of homogeneous gradients. In this paper the Stejskal-Tanner equation was derived for the general case on non-uniform diffusion gradients...
August 30, 2018: Journal of Magnetic Resonance
Karol Borkowski, Artur Tadeusz Krzyżak
The DTI-based tractography, despite its restrictions, is the most widely utilized fiber tracking method in clinical practice. Its fidelity is strictly dependent on the precision and accuracy of the DTI measurement, which in turn is limited by the linearity of the diffusion sensitizing gradient. The influence of the gradient distortions on the differences between the real and measured orientation of fibers was investigated by computer simulations. In addition, the potential of the b-matrix Spatial Distribution in DTI (BSD-DTI) technique in correcting such kind of errors was demonstrated experimentally...
August 30, 2018: Journal of Magnetic Resonance
Anna Bieber, Dennis Bücker, Malte Drescher
Nanometric distance measurements with EPR spectroscopy yield crucial information on the structure and interactions of macromolecules in complex systems. The range of suitable spin labels for such measurements was recently expanded with a new class of light-inducible labels: the triplet state of porphyrins. Importantly, accurate distance measurements between a triplet label and a nitroxide have been reported with two distinct light-induced spectroscopy techniques, (light-induced) triplet-nitroxide DEER (LiDEER) and laser-induced magnetic dipole spectroscopy (LaserIMD)...
August 29, 2018: Journal of Magnetic Resonance
Robert J Cooper, David W Prescott, Garrett J Lee, Karen L Sauer
An unshielded array of 87 Rb atomic magnetometers, operating close to 1 MHz, is used to attenuate interference by 42-48 dB. A sensitivity of 15 fT/Hz to a local source of signal is retained. In addition, a 2D spectroscopic technique, in which the magnetometers are repeatedly pumped and data acquired between pump times, enables a synchronously generated signal to be distinguished from an interfering signal very close in frequency; the timing and signal mimics what would be observed in a magnetic resonance echo train...
August 28, 2018: Journal of Magnetic Resonance
T Sakurai, S Kimura, M Kimata, H Nojiri, S Awaji, S Okubo, H Ohta, Y Uwatoko, K Kudo, Y Koike
We have developed a high-pressure electron spin resonance probe and successfully installed into the world's highest-field cryogen-free superconducting magnet having a maximum central field of 24.6 T. The high pressure of 2.5 GPa is achieved by the specially designed piston-cylinder pressure cell using THz-wave-transparent components. In the first application of this high-pressure high-field ESR system, we observed that the orthogonal dimer spin system SrCu2 (BO3 )2 undergoes a quantum phase transition from the dimer singlet ground to the plaquette singlet ground states...
August 23, 2018: Journal of Magnetic Resonance
Yaewon Kim, Mengxiao Liu, Christian Hilty
Dissolution dynamic nuclear polarization (D-DNP) is a powerful technique to improve NMR sensitivity by a factor of thousands. Combining D-DNP with NMR-based screening enables to mitigate solubility or availability problems of ligands and target proteins in drug discovery as it can lower the concentration requirements into the sub-micromolar range. One of the challenges that D-DNP assisted NMR screening methods face for broad application, however, is a reduced throughput due to additional procedures and time required to create hyperpolarization...
October 2018: Journal of Magnetic Resonance
Guohai Chen, Berg Dodson, Francis Johnson, Ileana Hancu, Eric Fiveland, Wanming Zhang, Craig Galligan, Christopher Puleo, Robert C Davis, Jeffrey Ashe, Richard R Vanfleet
Test disk electrodes were fabricated from carbon nanotubes (CNT) using the Carbon Nanotube Templated Microfabrication (CNT-M) technique. The CNT-M process uses patterned growth of carbon nanotube forests from surfaces to form complex patterns, enabling electrode sizing and shaping. The additional carbon infiltration process stabilizes these structures for further processing and handling. At a macroscopic scale, the electrochemical, electrical and magnetic properties, and magnetic resonance imaging (MRI) characteristics of the disk electrodes were investigated; their microstructure was also assessed...
October 2018: Journal of Magnetic Resonance
Rohan S Virgincar, Jerry Dahlke, Scott H Robertson, Nathann Morand, Yi Qi, Simone Degan, Bastiaan Driehuys, John C Nouls
Hyperpolarized (HP) 129 Xe MRI is emerging as a powerful, non-invasive method to image lung function and is beginning to find clinical application across a range of conditions. As clinical implementation progresses, it becomes important to translate back to well-defined animal models, where novel disease signatures can be characterized longitudinally and validated against histology. To date, preclinical 129 Xe MRI has been limited to only a few sites worldwide with 2D imaging that is not generally sufficient to fully capture the heterogeneity of lung disease...
October 2018: Journal of Magnetic Resonance
Andrew Cho, Roozbeh Eskandari, Vesselin Z Miloushev, Kayvan R Keshari
Although dissolution dynamic nuclear polarization is a robust technique to significantly increase magnetic resonance signal, the short T1 relaxation time of most 13 C-nuclei limits the timescale of hyperpolarized experiments. To address this issue, we have characterized a non-synthetic approach to extend the hyperpolarized lifetime of 13 C-nuclei in close proximity to solvent-exchangeable protons. Protons exhibit stronger dipolar relaxation than deuterium, so dissolving these compounds in D2 O to exchange labile protons with solvating deuterons results in longer-lived hyperpolarization of the 13 C-nucleus 2-bonds away...
October 2018: Journal of Magnetic Resonance
Daan W de Kort, Andi Reci, Nicholas P Ramskill, Matthias Appel, Hilko de Jong, Michael D Mantle, Andrew J Sederman, Lynn F Gladden
A method is presented for accelerating the acquisition of spatially-resolved displacement propagators via under-sampling of an Alternating Pulsed Gradient Stimulated Echo - Rapid Acquisition with Relaxation Enhancement (APGSTE-RARE) data acquisition with compressed sensing image reconstruction. The method was demonstrated with respect to the acquisition of 2D spatially-resolved displacement propagators of water flowing through a packed bed of hollow cylinders. The q,k-space was under-sampled according to variable-density pseudo-random sampling patterns...
October 2018: Journal of Magnetic Resonance
Hiroyuki Ueda, Hiroaki Seki, Yosuke Ito, Takenori Oida, Yo Taniguchi, Testsuo Kobayashi
We studied stimulus-induced rotary-saturation preparation (which enables measurement of oscillating magnetic fields using MRI) and derived an analytical solution of the Bloch equation to understand magnetization dynamics mathematically and comprehensively and to conduct simulations without sequential-calculation techniques such as the Runge-Kutta method. We formulated the dynamics using the Bloch equation, introducing an additional rotating frame and some approximations to make it into a homogeneous differential equation...
October 2018: Journal of Magnetic Resonance
Orane Lorton, Jean-Noël Hyacinthe, Stéphane Desgranges, Laura Gui, Antoine Klauser, Zarko Celicanin, Lindsey A Crowe, François Lazeyras, Eric Allémann, Nicolas Taulier, Christiane Contino-Pépin, Rares Salomir
OBJECTIVE: Perfluorocarbon nano- and micron-sized emulsions are a new field of investigation in cancer treatment due to their ability to be used as imaging contrast agents, or as delivery vectors for pharmaceuticals. They also demonstrated capability to enhance the efficiency of high intensity focused ultrasound thermo-therapy. In the context of new biomedical applications we investigated perfluorooctyl bromide (PFOB) theranostic droplets using 19 F NMR. Each droplet contains biocompatible fluorinated surfactants composed of a polar Tris(hydroxymethyl)aminomethane head unit and hydrophobic perfluorinated tail (abbreviated as F-TAC)...
October 2018: Journal of Magnetic Resonance
Stephan Rein, Philipp Lewe, Susana L Andrade, Sylwia Kacprzak, Stefan Weber
Pulsed electron-electron double resonance (PELDOR, alternatively called DEER for double electron-electron resonance) pulse sequences allow for the detection of echo decay curves that are modulated by dipole-dipole-coupling frequencies of interacting electron spins. With increasing distance between them, the echo decay needs to be monitored over a progressively extended time period. However, since the echo intensity typically falls off exponentially with increasing time, this might be problematic with respect to the minimum signal-to-noise ratio required for a sound data analysis...
October 2018: Journal of Magnetic Resonance
A A Sukhanov, R F Likerov, R M Eremina, I V Yatsyk, T P Gavrilova, V F Tarasov, Yu D Zavartsev, S A Kutovoi
The ESEEM spectroscopy was used to determine positions of the 143 Nd3+ impurity ions in Y2 SiO5 single crystal. It is established that neodymium ions substitute yttrium ions in the Y2 positions with seven nearest oxygen ions. Crystal field parameters of 143 Nd3+ impurity centers in isotopically pure Y2 28 SiO5 and Sc2 28 SiO5 single crystals were determined using data of CW EPR spectroscopy and the known energy level schemes.
October 2018: Journal of Magnetic Resonance
Pinelopi Moutzouri, Peter Kiraly, Mohammadali Foroozandeh, Andrew R Phillips, Steven R Coombes, Mathias Nilsson, Gareth A Morris
Diffusion-ordered spectroscopy (DOSY) is a valuable tool for the analysis of intact mixtures, since it can separate the signals of components according to their apparent diffusion coefficients. However, DOSY experiments are acutely sensitive to spectral quality, and especially to signal overlap, which can lead to misleading apparent diffusion coefficients. Here, we introduce a new NMR experiment to reduce signal overlap in mixtures with a wide range of concentrations, by removing one-bond 13 C satellites. In such high dynamic range mixtures, 13 C isotopomer signals from major components can overlap with signals from minor components, causing problematic distortions in the diffusion domain of a DOSY spectrum...
October 2018: Journal of Magnetic Resonance
Erika L Sesti, Edward P Saliba, Nicholas Alaniva, Alexander B Barnes
Dynamic nuclear polarization (DNP) can improve nuclear magnetic resonance (NMR) sensitivity by orders of magnitude. Polarizing agents containing unpaired electrons required for DNP can broaden nuclear resonances in the presence of appreciable hyperfine couplings. Here we present the first cross polarization experiments implemented with electron decoupling, which attenuates detrimental hyperfine couplings. We also demonstrate magic angle spinning (MAS) DNP experiments below 6 K, producing unprecedented nuclear spin polarization in rotating solids...
October 2018: Journal of Magnetic Resonance
Mihajlo Novakovic, Samuel F Cousin, Michael J Jaroszewicz, Rina Rosenzweig, Lucio Frydman
Cross-relaxation and isotropic mixing phenomena leading to the Nuclear Overhauser Effect (NOE) and to the TOCSY experiment, lie at the center of structural determinations by NMR. 2D TOCSY and NOESY exploit these polarization transfer effects to determine inter-site connectivities and molecular geometries under physiologically-relevant conditions. Among these sequences' drawback, particularly for the case of NOEs, are a lack of sensitivity arising from small structurally-relevant cross peaks. The present study explores the application of multiple Zeno-like projective measurements, to enhance the cross-peaks between spectrally distinct groups in proteins -in particular between amide and aliphatic protons...
September 2018: Journal of Magnetic Resonance
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