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Journal of Magnetic Resonance

Denis A Komarov, Hiroshi Hirata
In this paper, we introduce a procedure for the reconstruction of spectral-spatial EPR images using projections acquired with the constant sweep of a magnetic field. The application of a constant field-sweep and a predetermined data sampling rate simplifies the requirements for EPR imaging instrumentation and facilitates the backprojection-based reconstruction of spectral-spatial images. The proposed approach was applied to the reconstruction of a four-dimensional numerical phantom and to actual spectral-spatial EPR measurements...
May 17, 2017: Journal of Magnetic Resonance
Chong Duan, Colm Ryan, Shin Utsuzawa, Yi-Qiao Song, Martin D Hürlimann
Saturation-recovery measurements with Carr-Purcell-Meiboom-Gill sequences are commonly employed to measure the longitudinal relaxation time constant, T1, in grossly inhomogeneous fields. We show that in general the off-resonant effect generates unexpected extra signals in the T1 measurement. In the present study, we derive a modified T1 kernel that accounts for this off-resonance effect quantitatively. The new kernel has been tested with numerical simulations and experiments, and excellent agreement is found...
May 10, 2017: Journal of Magnetic Resonance
Pavel Svehla, Khieu-Van Nguyen, Jing-Rebecca Li, Luisa Ciobanu
High resolution Manganese Enhanced Magnetic Resonance Imaging (MEMRI), which uses manganese as a T1 contrast agent, has great potential for functional imaging of live neuronal tissue at single neuron scale. However, reaching high resolutions often requires long acquisition times which can lead to reduced image quality due to sample deterioration and hardware instability. Compressed Sensing (CS) techniques offer the opportunity to significantly reduce the imaging time. The purpose of this work is to test the feasibility of CS acquisitions based on Diffusion Limited Aggregation (DLA) sampling patterns for high resolution quantitative T1-weighted imaging...
May 9, 2017: Journal of Magnetic Resonance
Ilia Kaminker, Ryan Barnes, Songi Han
We report here on the implementation of arbitrary waveform generation (AWG) capabilities at ∼200GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7T. This is achieved with the integration of a 1GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at Ku-band frequencies with 1ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200GHz with >150mW power...
April 27, 2017: Journal of Magnetic Resonance
J Jokisaari, A M Kantola, J Vaara
In principle, all the NMR observables, spin-spin coupling J, nuclear shielding σ and quadrupole coupling q, are magnetic field-dependent. The field dependence may be classified into two categories: direct and indirect (apparent) dependence. The former arises from the magnetic field-induced deformation of the molecular electronic cloud, while the latter stems from a slightly anisotropic orientation distribution of molecules, due to the interaction between the anisotropy of the molecular susceptibility tensor and the external magnetic field...
April 26, 2017: Journal of Magnetic Resonance
Sandeep Kumar Mishra, N Suryaprakash
Poor chemical shift dispersion and pairwise interaction among the entire coupled network of spins results in complex one dimensional (1)H NMR spectra, severely hampering the analysis and the accurate determination of (n)JHH. Available two dimensional selective refocusing based techniques suffer from the evolution of undesirable couplings and intense axial peaks, creating ambiguity in the analysis and the extraction of coupling values. In this work, we report a novel two dimensional experiment for the complete elimination of axial peaks and unwanted couplings, while retaining only the couplings of the selected proton to its partners, with a blend of ultra-high resolution achieved by real time broad band homonuclear decoupling...
April 25, 2017: Journal of Magnetic Resonance
Ēriks Kupče, Bernd Wrackmeyer
We propose a (13)C detected experiment, the (H)CNMQC pulse sequence for measuring one-bond and long-range (15)N(13)C scalar coupling constants in small organic molecules at the natural isotopic abundance. The previously proposed (1)H detected H(C)NMBC experiment performs poorly in situations where the carbon atom of interest has no attached protons, in the presence of splittings due to the homonuclear HH couplings, unwanted coherence leaks and considerable t1-noise. These problems are largely avoided in the (H)CNMQC experiment based on direct (13)C detection...
April 25, 2017: Journal of Magnetic Resonance
Andrew McDowell, Mark Conradi
An NMR shim coil design method that addresses the severe spatial constraints of miniaturized dipole magnets is introduced. The fundamental design element, a collection of straight wires, is shown to be sufficient for producing a complete set of shim fields of high mathematical order. In accord with these theoretical considerations, a shim set is constructed using four wires in each of four directions to create all first through fourth order fields, except one. This shim set, with its supporting structure, occupies only 2mm of the available 5mm gap in a small 1...
April 24, 2017: Journal of Magnetic Resonance
Eric Van Reeth, Hélène Ratiney, Michael Tesch, Denis Grenier, Olivier Beuf, Steffen J Glaser, Dominique Sugny
This work investigates the use of MRI radio-frequency (RF) pulses designed within the framework of optimal control theory for image contrast optimization. The magnetization evolution is modeled with Bloch equations, which defines a dynamic system that can be controlled via the application of the Pontryagin Maximum Principle (PMP). This framework allows the computation of optimal RF pulses that bring the magnetization to a given state to obtain the desired contrast after acquisition. Creating contrast through the optimal manipulation of Bloch equations is a new way of handling contrast in MRI, which can explore the theoretical limits of the system...
April 21, 2017: Journal of Magnetic Resonance
J Möser, K Lips, M Tseytlin, G R Eaton, S S Eaton, A Schnegg
X-band rapid-scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid-scan and continuous-wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid-scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid-scan EPR results in signal-to-noise improvements by factors between 10 and 50. Rapid-scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude...
April 17, 2017: Journal of Magnetic Resonance
Oleg V Petrov, Siegfried Stapf
This work addresses the problem of a compact and easily comparable representation of multi-exponential relaxation data. It is often convenient to describe such data in a few parameters, all being of physical significance and easy to interpret, and in such a way that enables a model-free comparison between different groups of samples. Logarithmic moments (LMs) of the relaxation time constitute a set of parameters which are related to the characteristic relaxation time on the log-scale, the width and the asymmetry of an underlying distribution of exponentials...
April 13, 2017: Journal of Magnetic Resonance
Andraž Krajnc, Bart Bueken, Dirk De Vos, Gregor Mali
Nuclear magnetic resonance spectroscopy combined with modeling represents a powerful tool for the structural analysis of heterogeneous materials. In this contribution we describe an upgraded method, particularly suited for the structural analysis of mixed-linker metal-organic framework materials, which is based on the measurement and modeling of proton spin diffusion among constituents. We tested the method on a UiO-66-type metal-organic material, in which the organic building units were 1,4-benzenedicarboxylate and trans-1,4-cyclohexanedicarboxylate anions distributed within the framework in an unknown manner...
April 12, 2017: Journal of Magnetic Resonance
Qi Wang, Renjing Gao, Shutian Liu
This paper presents a topology optimization based design method for the design of unilateral nuclear magnetic resonance (NMR), with which a remote homogeneous field can be obtained. The topology optimization is actualized by seeking out the optimal layout of ferromagnetic materials within a given design domain. The design objective is defined as generating a sensitive magnetic field with optimal homogeneity and maximal field strength within a required region of interest (ROI). The sensitivity of the objective function with respect to the design variables is derived and the method for solving the optimization problem is presented...
April 9, 2017: Journal of Magnetic Resonance
Marianne Cleve, Martin Krämer, Alexander Gussew, Jürgen R Reichenbach
Phase and frequency corrections of magnetic resonance spectroscopic data are of major importance to obtain reliable and unambiguous metabolite estimates as validated in recent research for single-shot scans with the same spectral fingerprint. However, when using the J-difference editing technique (1)H MEGA-PRESS, misalignment between mean edited (ON‾) and non-edited (OFF‾) spectra that may remain even after correction of the corresponding individual single-shot scans results in subtraction artefacts compromising reliable GABA quantitation...
April 7, 2017: Journal of Magnetic Resonance
Chang-Hoon Choi, Suk-Min Hong, YongHyun Ha, N Jon Shah
A double-tuned (1)H/(19)F coil using PIN-diode switches was developed and its performance evaluated. The is a key difference from the previous developments being that this design used a PIN-diode switch in series with an additionally inserted inductor in parallel to one of the capacitors on the loop. The probe was adjusted to (19)F when the reverse bias voltage was applied (PIN-diode OFF), whilst it was switched to (1)H when forward current was flowing (PIN-diode ON). S-parameters and Q-factors of single- and double-tuned coils were examined and compared with/without a phantom on the bench...
April 7, 2017: Journal of Magnetic Resonance
Sebastian Vellmer, Daniel Edelhoff, Dieter Suter, Ivan I Maximov
Diffusion MRI is an efficient and widely used technique for the investigation of tissue structure and organisation in vivo. Multiple phenomenological and biophysical diffusion models are intensively exploited for the analysis of the diffusion experiments. However, the verification of the applied diffusion models remains challenging. In order to provide a "gold standard" and to assess the accuracy of the derived parameters and the limitations of the diffusion models, anisotropic diffusion phantoms with well known architecture are demanded...
April 5, 2017: Journal of Magnetic Resonance
Jeffrey C Hoch
Non-Fourier methods of spectrum analysis are gaining traction in NMR spectroscopy, driven by their utility for processing nonuniformly sampled data. These methods afford new opportunities for optimizing experiment time, resolution, and sensitivity of multidimensional NMR experiments, but they also pose significant challenges not encountered with the discrete Fourier transform. A brief history of non-Fourier methods in NMR serves to place different approaches in context. Non-Fourier methods reflect broader trends in the growing importance of computation in NMR, and offer insights for future software development...
March 27, 2017: Journal of Magnetic Resonance
Gabriele Stevanato, James Eills, Christian Bengs, Giuseppe Pileio
We have recently demonstrated, in the context of para-hydrogen induced polarization (PHIP), the conversion of hyperpolarized proton singlet order into heteronuclear magnetisation can be efficiently achieved via a new sequence named S2hM (Singlet to heteronuclear Magnetisation). In this paper we give a detailed theoretical description, supported by an experimental illustration, of S2hM. Theory and experiments on thermally polarized samples demonstrate the proposed method is robust to frequency offset mismatches and radiofrequency field inhomogeneities...
March 6, 2017: Journal of Magnetic Resonance
Victor D Schepkin, Andreas Neubauer, Armin M Nagel, Thomas F Budinger
Potassium and sodium specific binding in vivo were explored at 21.1T by triple quantum (TQ) magnetic resonance (MR) signals without filtration to achieve high sensitivities and precise quantifications. The pulse sequence used time proportional phase increments (TPPI). During simultaneous phase-time increments, it provided total single quantum (SQ) and TQ MR signals in the second dimension at single and triple quantum frequencies, respectively. The detection of both TQ and SQ signals was performed at identical experimental conditions and the resulting TQ signal equals 60±3% of the SQ signal when all ions experience sufficient time for binding...
March 6, 2017: Journal of Magnetic Resonance
Michael C D Tayler, Dimitrios Sakellariou
We present designs for compact, inexpensive and strong dipole permanent magnets aimed primarily at magnetic resonance applications where prepolarization and detection occur at different locations. Low-homogeneity magnets with a 7.5mm bore size and field up to nearly 2T 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 1mL of pure [(13)C]-methanol prior to detection of its high-resolution NMR spectrum at zero field (measurement field below 10(-10)T), where signals appear at multiples of the carbon-hydrogen spin-spin coupling frequency (1)JCH=140...
March 6, 2017: Journal of Magnetic Resonance
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