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Journal of Magnetic Resonance

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https://www.readbyqxmd.com/read/28088651/limitations-in-biexponential-fitting-of-nmr-inversion-recovery-curves
#1
Mohammed Salman Shazeeb, Christopher H Sotak
NMR relaxation agents have long been employed as contrast agents in MRI. In many cases, the contrast agent is confined to either (i) the vascular and/or extracellular compartment (EC), as is the case with gadolinium(III)-based agents, or (ii) the intracellular compartment (IC), as is the case with manganese(II) ions. The compartmentalization of contrast agents often results in tissue-water (1)H relaxation profiles that are well modeled as biexponential. It has long been recognized that water exchange between compartments modifies the biexponential relaxation parameters (amplitudes and rate constants) from those that would be found in the absence of exchange...
January 6, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28086185/attenuation-of-the-nmr-signal-in-a-field-gradient-due-to-stochastic-dynamics-with-memory
#2
Vladimír Lisý, Jana Tóthová
The attenuation function S(t) for an ensemble of spins in a magnetic-field gradient is calculated by accumulation of the phase shifts in the rotating frame resulting from the displacements of spin-bearing particles. The found S(t), expressed through the particle mean square displacement, is applicable for any kind of stationary stochastic motion of spins, including their non-markovian dynamics with memory. The known expressions valid for normal and anomalous diffusion are obtained as special cases in the long time approximation...
January 5, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28081476/electron-spin-relaxation-of-a-boron-containing-heterocyclic-radical
#3
Sandra S Eaton, Kirby Huber, Hanan Elajaili, Joseph McPeak, Gareth R Eaton, Lauren E Longobardi, Douglas W Stephan
Preparation of the stable boron-containing heterocyclic phenanthrenedione radical, (C6F5)2B(O2C14H8), by frustrated Lewis pair chemistry has been reported recently. Electron paramagnetic resonance measurements of this radical were made at X-band in toluene:dichloromethane (9:1) from 10 to 293K, in toluene from 180 to 293K and at Q-band at 80K. In well-deoxygenated 0.1mM toluene solution at room temperature hyperfine splittings from (11)B, four pairs of (1)H, and 5 pairs of (19)F contribute to an EPR spectrum with many resolved lines...
December 30, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28073068/comparative-analysis-of-isotropic-diffusion-weighted-imaging-sequences
#4
Sebastian Vellmer, Rüdiger Stirnberg, Daniel Edelhoff, Dieter Suter, Tony Stöcker, Ivan I Maximov
Visualisation of living tissue structure and function is a challenging problem of modern imaging techniques. Diffusion MRI allows one to probe in vivo structures on a micrometer scale. However, conventional diffusion measurements are time-consuming procedures, because they require several measurements with different gradient directions. Considerable time savings are therefore possible by measurement schemes that generate an isotropic diffusion weighting in a single shot. Multiple approaches for generating isotropic diffusion weighting are known and have become very popular as useful tools in clinical research...
December 30, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28064071/enhanced-efficiency-of-solid-state-nmr-investigations-of-energy-materials-using-an-external-automatic-tuning-matching-eatm-robot
#5
Oliver Pecher, David M Halat, Jeongjae Lee, Zigeng Liu, Kent J Griffith, Marco Braun, Clare P Grey
We have developed and explored an external automatic tuning/matching (eATM) robot that can be attached to commercial and/or home-built magic angle spinning (MAS) or static nuclear magnetic resonance (NMR) probeheads. Complete synchronization and automation with Bruker and Tecmag spectrometers is ensured via transistor-transistor-logic (TTL) signals. The eATM robot enables an automated "on-the-fly" re-calibration of the radio frequency (rf) carrier frequency, which is beneficial whenever tuning/matching of the resonance circuit is required, e...
December 23, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28043004/a-simple-and-low-cost-permanent-magnet-system-for-nmr
#6
K Chonlathep, T Sakamoto, K Sugahara, Y Kondo
We have developed a simple, easy to build, and low-cost magnet system for NMR, of which homogeneity is about 4×10(-4) at 57mT, with a pair of two commercially available ferrite magnets. This homogeneity corresponds to about 90Hz spectral resolution at 2.45MHz of the hydrogen Larmor frequency. The material cost of this NMR magnet system is little more than $100. The components can be printed by a 3D printer.
December 23, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28061381/hyperpolarized-13-c-pyruvate-mouse-brain-metabolism-with-absorptive-mode-epsi-at-1t
#7
Vesselin Z Miloushev, Valentina Di Gialleonardo, Lucia Salamanca-Cardona, Fabian Correa, Kristin L Granlund, Kayvan R Keshari
The expected signal in echo-planar spectroscopic imaging experiments was explicitly modeled jointly in spatial and spectral dimensions. Using this as a basis, absorptive-mode type detection can be achieved by appropriate choice of spectral delays and post-processing techniques. We discuss the effects of gradient imperfections and demonstrate the implementation of this sequence at low field (1.05T), with application to hyperpolarized [1-(13)C] pyruvate imaging of the mouse brain. The sequence achieves sufficient signal-to-noise to monitor the conversion of hyperpolarized [1-(13)C] pyruvate to lactate in the mouse brain...
December 21, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28040623/multidimensional-diffusion-mri
#8
Daniel Topgaard
Principles from multidimensional NMR spectroscopy, and in particular solid-state NMR, have recently been transferred to the field of diffusion MRI, offering non-invasive characterization of heterogeneous anisotropic materials, such as the human brain, at an unprecedented level of detail. Here we revisit the basic physics of solid-state NMR and diffusion MRI to pinpoint the origin of the somewhat unexpected analogy between the two fields, and provide an overview of current diffusion MRI acquisition protocols and data analysis methods to quantify the composition of heterogeneous materials in terms of diffusion tensor distributions with size, shape, and orientation dimensions...
December 19, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28024258/phase-incremented-echo-train-acquisition-applied-to-magnetic-resonance-pore-imaging
#9
S A Hertel, P Galvosas
Efficient phase cycling schemes remain a challenge for NMR techniques if the pulse sequences involve a large number of rf-pulses. Especially complex is the Carr Purcell Meiboom Gill (CPMG) pulse sequence where the number of rf-pulses can range from hundreds to several thousands. Our recent implementation of Magnetic Resonance Pore Imaging (MRPI) is based on a CPMG rf-pulse sequence in order to refocus the effect of internal gradients inherent in porous media. While the spin dynamics for spin-1/2 systems in CPMG like experiments are well understood it is still not straight forward to separate the desired pathway from the spectrum of unwanted coherence pathways...
December 16, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28024256/%C3%AE-vip-customized-virtual-phantom-for-quantitative-magnetic-resonance-micro-imaging-at-high-magnetic-field
#10
C Rondeau-Mouro, R Kovrlija, G Gambarota, H Saint-Jalmes
The applications of Magnetic Resonance micro-Imaging (MRμI) cover nowadays a wide range of fields. However few of them present quantitative measurements when the sample of interest changes over time or in case of a long acquisition time. In this domain, two challenges have to be overcome: the introduction of a phantom as a reference signal and the guarantee that this signal is stable over the experiment duration while some conditions such as temperature and/or the moisture are varied. The aim of the present study was to implement a dedicated experimental set-up to generate a virtual phantom (ViP) signal in a vertical-bore 11...
December 11, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28024257/evaluation-of-sandstone-surface-relaxivity-using-laser-induced-breakdown-spectroscopy
#11
Kathryn E Washburn, Magdalena Sandor, Yuesheng Cheng
Nuclear magnetic resonance (NMR) relaxometry is a common technique used to assess the pore size of fluid-filled porous materials in a wide variety of fields. However, the NMR signal itself only provides a relative distribution of pore size. To calculate an absolute pore size distribution from the NMR data, the material's surface relaxivity needs to be known. Here, a method is presented using laser-induced breakdown spectroscopy (LIBS) to evaluate surface relaxivity in sandstones. NMR transverse and longitudinal relaxation was measured on a set of sandstone samples and the surface relaxivity was calculated from the pore size distribution determined with MICP measurements...
December 9, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28006675/the-inversion-of-2d-nmr-relaxometry-data-using-l1-regularization
#12
Xiaolong Zhou, Guanqun Su, Lijia Wang, Shengdong Nie, Xinmin Ge
NMR relaxometry has been used as a powerful tool to study molecular dynamics. Many algorithms have been developed for the inversion of 2D NMR relaxometry data. Unlike traditional algorithms implementing L2 regularization, high order Tikhonov regularization or iterative regularization, L1 penalty term is involved to constrain the sparsity of resultant spectra in this paper. Then fast iterative shrinkage-thresholding algorithm (FISTA) is proposed to solve the L1 regularization problem. The effectiveness, noise vulnerability and practical utility of the proposed algorithm are analyzed by simulations and experiments...
December 9, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28012297/balanced-steady-state-free-precession-bssfp-from-an-effective-field-perspective-application-to-the-detection-of-chemical-exchange-bssfpx
#13
Shu Zhang, Zheng Liu, Aaron Grant, Jochen Keupp, Robert E Lenkinski, Elena Vinogradov
Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence...
December 8, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27992783/orthogonal-spin-labeling-using-click-chemistry-for-in-vitro-and-in-vivo-applications
#14
Svetlana Kucher, Sergei Korneev, Swati Tyagi, Ronja Apfelbaum, Dina Grohmann, Edward A Lemke, Johann P Klare, Heinz-Jürgen Steinhoff, Daniel Klose
Site-directed spin labeling for EPR- and NMR spectroscopy has mainly been achieved exploiting the specific reactivity of cysteines. For proteins with native cysteines or for in vivo applications, an alternative coupling strategy is required. In these cases click chemistry offers major benefits by providing a fast and highly selective, biocompatible reaction between azide and alkyne groups. Here, we establish click chemistry as a tool to target unnatural amino acids in vitro and in vivo using azide- and alkyne-functionalized spin labels...
December 2, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28012298/s-3-hmbc-hetero-spin-state-selective-hmbc-for-accurate-measurement-of-long-range-heteronuclear-coupling-constants
#15
Casper Hoeck, Charlotte H Gotfredsen, Ole W Sørensen
A novel method, Spin-State-Selective (S(3)) HMBC hetero, for accurate measurement of heteronuclear coupling constants is introduced. The method extends the S(3) HMBC technique for measurement of homonuclear coupling constants by appending a pulse sequence element that interchanges the polarization in (13)C-(1)H methine pairs. This amounts to converting the spin-state selectivity from (1)H spin states to (13)C spin states in the spectra of long-range coupled (1)H spins, allowing convenient measurement of heteronuclear coupling constants similar to other S(3) or E...
December 1, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27960105/evaluation-and-comparison-of-diffusion-mr-methods-for-measuring-apparent-transcytolemmal-water-exchange-rate-constant
#16
Xin Tian, Hua Li, Xiaoyu Jiang, Jingping Xie, John C Gore, Junzhong Xu
Two diffusion-based approaches, CG (constant gradient) and FEXI (filtered exchange imaging) methods, have been previously proposed for measuring transcytolemmal water exchange rate constant kin, but their accuracy and feasibility have not been comprehensively evaluated and compared. In this work, both computer simulations and cell experiments in vitro were performed to evaluate these two methods. Simulations were done with different cell diameters (5, 10, 20μm), a broad range of kin values (0.02-30s(-1)) and different SNR's, and simulated kin's were directly compared with the ground truth values...
December 1, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27951427/anisotropic-phantom-to-calibrate-high-q-diffusion-mri-methods
#17
M E Komlosh, D Benjamini, A S Barnett, V Schram, F Horkay, A V Avram, P J Basser
A silicon oil-filled glass capillary array is proposed as an anisotropic diffusion MRI phantom. Together with a computational/theoretical pipeline these provide a gold standard for calibrating and validating high-q diffusion MRI experiments. The phantom was used to test high angular resolution diffusion imaging (HARDI) and double pulsed-field gradient (d-PFG) MRI acquisition schemes. MRI-based predictions of microcapillary diameter using both acquisition schemes were compared with results from optical microscopy...
November 30, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27951425/quantitative-nmr-spectroscopy-for-gas-analysis-for-production-of-primary-reference-gas-mixtures
#18
K Meyer, K Rademann, U Panne, M Maiwald
Due to its direct correlation to the number of spins within a sample quantitative NMR spectroscopy (qNMR) is a promising method with absolute comparison abilities in complex systems in technical, as well as metrological applications. Most of the samples studied with qNMR are in liquid state in diluted solutions, while gas-phase applications represent a rarely applied case. Commercially available NMR equipment was used for purity assessment of liquid and liquefied hydrocarbons serving as raw materials for production of primary reference gas standards...
November 27, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27951426/stacked-magnetic-resonators-for-mri-rf-coils-decoupling
#19
Elodie Georget, Michel Luong, Alexandre Vignaud, Eric Giacomini, Edouard Chazel, Guillaume Ferrand, Alexis Amadon, Franck Mauconduit, Stefan Enoch, Gérard Tayeb, Nicolas Bonod, Cyril Poupon, Redha Abdeddaim
Parallel transmission is a very promising method to tackle B1(+) field inhomogeneities at ultrahigh field in magnetic resonant imaging (MRI). This technique is however limited by the mutual coupling between the radiating elements. Here we propose to solve this problem by designing a passive magneto-electric resonator that we here refer to as stacked magnetic resonator (SMR). By combining numerical and experimental methodologies, we prove that this novelty passive solution allows an efficient decoupling of elements of a phased-array coil...
November 21, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27821291/development-of-ultrafast-ute-imaging-for-granular-systems
#20
Hilary T Fabich, Andrew J Sederman, Daniel J Holland
Ultrashort echo time (UTE) imaging is commonly used in medical MRI to image 'solid' types of tissue; to date it has not been widely used in engineering or materials science, in part due to the relatively long imaging times required. Here we show how the acquisition time for UTE can be reduced to enable a preliminary study of a fluidized bed, a type of reactor commonly used throughout industry containing short T2(∗) material and requiring fast imaging. We demonstrate UTE imaging of particles with a T2(∗) of only 185μs, and an image acquisition time of only 25ms...
October 29, 2016: Journal of Magnetic Resonance
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