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NMR in Biomedicine

Jens H Jensen, Emilie T McKinnon, G Russell Glenn, Joseph A Helpern
In order to quantify well-defined microstructural properties of brain tissue from diffusion MRI (dMRI) data, tissue models are typically employed that relate biological features, such as cell morphology and cell membrane permeability, to the diffusion dynamics. A variety of such models have been proposed for white matter, and their validation is a topic of active interest. In this paper, three different tissue models are tested by comparing their predictions for a specific microstructural parameter to a value measured independently with a recently proposed dMRI method known as fiber ball imaging (FBI)...
January 13, 2017: NMR in Biomedicine
Florian Schubert, Simone Kühn, Jürgen Gallinat, Ralf Mekle, Bernd Ittermann
The amygdala plays a key role in emotional learning and in the processing of emotions. As disturbed amygdala function has been linked to several psychiatric conditions, a knowledge of its biochemistry, especially neurotransmitter levels, is highly desirable. The spin echo full intensity acquired localized (SPECIAL) sequence, together with a transmit/receive coil, was used to perform very short-TE magnetic resonance spectroscopy at 3 T to determine the neurochemical profile in a spectroscopic voxel containing the amygdala in 21 healthy adult subjects...
January 6, 2017: NMR in Biomedicine
Meher R Juttukonda, Lori C Jordan, Melissa C Gindville, Larry T Davis, Jennifer M Watchmaker, Sumit Pruthi, Manus J Donahue
Sickle cell anemia (SCA) is a genetic disorder resulting in reduced oxygen carrying capacity and elevated stroke risk. Pseudo-continuous arterial spin labeling (pCASL) measures of cerebral blood flow (CBF) may have relevance for stroke risk assessment; however, the effects of elevated flow velocity and reduced bolus arrival time (BAT) on CBF quantification in SCA patients have not been thoroughly characterized, and pCASL model parameters used in healthy adults are often applied to patients with SCA. Here, cervical arterial flow velocities and pCASL labeling efficiencies were computed in adults with SCA (n = 19) and age- and race-matched controls without sickle trait (n = 7) using pCASL in sequence with phase contrast MR angiography (MRA)...
January 4, 2017: NMR in Biomedicine
Mohammad Ali Parto Dezfouli, Mohsen Parto Dezfouli, Alireza Ahmadian, Alejandro F Frangi, Melika Esmaeili Rad, Hamidreza Saligheh Rad
MRS is an analytical approach used for both quantitative and qualitative analysis of human body metabolites. The accurate and robust quantification capability of proton MRS ((1) H-MRS) enables the accurate estimation of living tissue metabolite concentrations. However, such methods can be efficiently employed for quantification of metabolite concentrations only if the overlapping nature of metabolites, existing static field inhomogeneity and low signal-to-noise ratio (SNR) are taken into consideration. Representation of (1) H-MRS signals in the time-frequency domain enables us to handle the baseline and noise better...
January 4, 2017: NMR in Biomedicine
Wybe J M van der Kemp, Bertine L Stehouwer, Vincent O Boer, Peter R Luijten, Dennis W J Klomp, Jannie P Wijnen
In vivo water- and fat-suppressed (1) H magnetic resonance spectroscopy (MRS) and (31) P magnetic resonance adiabatic multi-echo spectroscopic imaging were performed at 7 T in duplicate in healthy fibroglandular breast tissue of a group of eight volunteers. The transverse relaxation times of (31) P metabolites were determined, and the reproducibility of (1) H and (31) P MRS was investigated. The transverse relaxation times for phosphoethanolamine (PE) and phosphocholine (PC) were fitted bi-exponentially, with an added short T2 component of 20 ms for adenosine monophosphate, resulting in values of 199 ± 8 and 239 ± 14 ms, respectively...
December 28, 2016: NMR in Biomedicine
Hwon Heo, Jae-Bum Ahn, Hyeong Hun Lee, Euna Kwon, Jun-Won Yun, Hyeonjin Kim, Byeong-Cheol Kang
Given the strong coupling between the substantia nigra (SN) and striatum (STR) in the early stage of Parkinson's disease (PD), yet only a few studies reported to date that have simultaneously investigated the neurochemistry of these two brain regions in vivo, we performed longitudinal metabolic profiling in the SN and STR of 1-methyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated common marmoset monkey models of PD (n = 10) by using proton MRS ((1) H-MRS) at 9.4 T. T2 relaxometry was also performed in the SN by using MRI...
December 28, 2016: NMR in Biomedicine
N I Avdievich, J Hoffmann, G Shajan, A Pfrommer, I A Giapitzakis, K Scheffler, A Henning
Ultra-high field (UHF, ≥7 T) tight fit transceiver phased arrays improve transmit (Tx) efficiency (B1(+) /√P) in comparison with Tx-only arrays, which are usually larger to fit receive (Rx)-only arrays inside. One of the major problems limiting applications of tight fit arrays at UHFs is the anticipated increase of local tissue heating, which is commonly evaluated by the local specific absorption rate (SAR). To investigate the tradeoff between Tx efficiency and SAR when a tight fit UHF human head transceiver phased array is used instead of a Tx-only/Rx-only RF system, a single-row eight-element prototype of a 400 MHz transceiver head phased array was constructed...
December 28, 2016: NMR in Biomedicine
Fernando N Nogueira, Rui A Carvalho
The metabolic profile of major salivary glands was evaluated by (13) C nuclear magnetic resonance isotopomer analysis ((13) C NMR-IA) following the infusion of [U-(13) C]glucose in order to define the true metabolic character of submandibular (SM) and parotid (PA) glands at rest and during salivary stimulation, and to determine the metabolic remodeling driven by diabetes. In healthy conditions, the SM gland is characterized at rest by a glycolytic metabolic profile and extensive pyruvate cycling. On the contrary, the PA gland, although also dominated by glycolysis, also possesses significant Krebs' cycle activity and does not sustain extensive pyruvate cycling...
December 26, 2016: NMR in Biomedicine
Ting Yin, Ronald Peeters, Yuanbo Feng, Yewei Liu, Jie Yu, Steven Dymarkowski, Uwe Himmelreich, Raymond Oyen, Yicheng Ni
The purpose of this study was to investigate the reliability of 3D isotropic MRI and quantitative multi-parametric MRI characterization on an orthotopic pancreatic head tumor model in rats. 3D isotropic T2 -weighted MRI was performed as a routine for tumor longitudinal follow-up and volume estimation. Common bile duct diameter was measured from 3D multiplanar reconstruction. Quantitative multi-parametric measurements including pixel-wise T2 , T1 relaxivity, apparent diffusion coefficient (ADC) and apparent diffusion kurtosis mapping were performed twice throughout tumor growth...
December 23, 2016: NMR in Biomedicine
Ralf Mekle, Simone Kühn, Harald Pfeiffer, Semiha Aydin, Florian Schubert, Bernd Ittermann
The two-fold benefit of (1) H magnetic resonance spectroscopy (MRS) at high B0 fields - enhanced sensitivity and increased spectral dispersion - has been used previously to study dynamic changes in metabolite concentrations in the human brain in response to visual stimulation. In these studies, a strong visual on/off stimulus was combined with MRS data acquisition in a voxel location in the occipital cortex determined by an initial functional magnetic resonance imaging experiment. However, 1) to exclude the possibility of systemic effects (heartbeat, blood flow, etc...
December 23, 2016: NMR in Biomedicine
Keshav Datta, Daniel M Spielman
Hyperpolarized (13) C MRS allows in vivo interrogation of key metabolic pathways, with pyruvate (Pyr) the substrate of choice for current clinical studies. Knowledge of the liquid-state polarization is needed for full quantitation, and asymmetry of the C2 doublet, arising from 1% naturally abundant [1,2-(13) C]Pyr in any hyperpolarized [1-(13) C]Pyr sample, has been suggested as a direct measure of in vivo C1 polarization via the use of an in vitro calibration curve. Here we show that different polarization levels can yield the same C2 -doublet asymmetry, thus limiting the utility of this metric for quantitation...
December 22, 2016: NMR in Biomedicine
Colleen Bailey, Bernard Siow, Eleftheria Panagiotaki, John H Hipwell, Thomy Mertzanidou, Julie Owen, Patrycja Gazinska, Sarah E Pinder, Daniel C Alexander, David J Hawkes
The diffusion signal in breast tissue has primarily been modelled using apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM) and diffusion tensor (DT) models, which may be too simplistic to describe the underlying tissue microstructure. Formalin-fixed breast cancer samples were scanned using a wide range of gradient strengths, durations, separations and orientations. A variety of one- and two-compartment models were tested to determine which best described the data. Models with restricted diffusion components and anisotropy were selected in most cancerous regions and there were no regions in which conventional ADC or DT models were selected...
December 21, 2016: NMR in Biomedicine
Lauri Juhani Lehto, Alejandra Sierra, Olli Gröhn
Traumatic brain injury (TBI) is associated with various neurocognitive deficits, and rapid assessment of the damage is potentially important for the prevention and treatment of these deficits. Imaging assessment of mild or moderate damage outside the primary lesion area after TBI, however, remains challenging. Magnetization transfer (MT) has clearly been underutilized in imaging the damage caused by TBI. Here, we applied the MT ratio (MTR) using sweep imaging with Fourier transformation (SWIFT) to study microstructural tissue damage in the thalamocortical pathway outside the primary lesion in a lateral fluid percussion injury rat model of TBI, 5 months after injury...
December 16, 2016: NMR in Biomedicine
Zuohua Tang, Lingjie Wu, Zebin Xiao, Xiaoyuan Feng, Xinghuai Sun, Weijun Tang, Jie Wang, Lixin Jin
This study aimed to explore the optimal dose and manner of administration for visualization of the auditory pathway on manganese-enhanced MRI (ME MRI). Twenty-four healthy male Sprague-Dawley rats were randomly divided into three experimental groups (n = 8 for Groups A, B and C). The rats in Groups A, B and C were subjected to MnCl2 injection through the tympanum, inner ear endolymph and perilymph, respectively (0.2 M for four rats and 0.4 M for the others in each group) and observed at 1, 2, 3, 4, 7 and 10 days after the operation with 3...
December 15, 2016: NMR in Biomedicine
Sarah Eskreis-Winkler, Yan Zhang, Jingwei Zhang, Zhe Liu, Alexey Dimov, Ajay Gupta, Yi Wang
Quantitative susceptibility mapping (QSM) is an MR technique that depicts and quantifies magnetic susceptibility sources. Mapping iron, the dominant susceptibility source in the brain, has many important clinical applications. Herein, we review QSM applications in the diagnosis, medical management, and surgical treatment of disease. To assist in early disease diagnosis, QSM can identify elevated iron levels in the motor cortex of amyotrophic lateral sclerosis patients, in the substantia nigra of Parkinson's disease (PD) patients, in the globus pallidus, putamen, and caudate of Huntington's disease patients, and in the basal ganglia of Wilson's disease patients...
December 1, 2016: NMR in Biomedicine
Dmitriy A Yablonskiy, Alexander L Sukstanskii
Quantitative susceptibility mapping is a potentially powerful technique for mapping tissue magnetic susceptibility from gradient recalled echo (GRE) MRI signal phase. In this review, we present up-to-date theoretical developments in analyzing the relationships between GRE signal phase and the underlying tissue microstructure and magnetic susceptibility at the cellular level. Two important phenomena contributing to the GRE signal phase are at the focus of this review - tissue structural anisotropy (e.g. cylindrical axonal bundles in white matter) and magnetic susceptibility anisotropy...
November 11, 2016: NMR in Biomedicine
Valentina Mazzoli, Jos Oudeman, Klaas Nicolay, Mario Maas, Nico Verdonschot, Andre M Sprengers, Aart J Nederveen, Martijn Froeling, Gustav J Strijkers
In this study we investigated the changes in fiber length and diffusion parameters as a consequence of passive lengthening and stretching of the calf muscles. We hypothesized that changes in radial diffusivity (RD) are caused by changes in the muscle fiber cross sectional area (CSA) as a consequence of lengthening and shortening of the muscle. Diffusion Tensor MRI (DT-MRI) measurements were made twice in five healthy volunteers, with the foot in three different positions (30° plantarflexion, neutral position and 15° dorsiflexion)...
November 8, 2016: NMR in Biomedicine
Marta Tibiletti, Andrea Bianchi, Detlef Stiller, Volker Rasche
Blood perfusion in lung parenchyma is an important property for assessing lung function. In small animals, its quantitation is limited even with radioactive isotopes or dynamic contrast-enhanced MRI techniques. In this study, the feasibility flow-sensitive alternating inversion recovery (FAIR) for the quantification of blood flow in lung parenchyma in free breathing rats at 7 T has been investigated. In order to obtain sufficient signal from the short T2 * lung parenchyma, a 2D ultra-short echo time (UTE) Look-Locker read-out has been implemented...
November 3, 2016: NMR in Biomedicine
Shailesh B Raval, Tiejun Zhao, Narayanan Krishnamurthy, Tales Santini, Cynthia Britton, Vijay S Gorantla, Tamer S Ibrahim
The purpose of this study is to develop and evaluate a custom-designed 7  T MRI coil and explore its use for upper extremity applications. An RF system composed of a transverse electromagnetic transmit coil and an eight-channel receive-only array was developed for 7  T upper extremity applications. The RF system was characterized and evaluated using scattering parameters and B1(+) mapping. Finite difference time domain simulations were performed to evaluate the B1(+) field distribution and specific absorption rate for the forearm region of the upper extremity...
November 3, 2016: NMR in Biomedicine
Rita Gil, Diana Khabipova, Marcel Zwiers, Tom Hilbert, Tobias Kober, José P Marques
Diffusion-weighted imaging (DWI) provides information that allows the estimation of white-matter (WM) fibre orientation and distribution, but it does not provide information about myelin density, fibre concentration or fibre size within each voxel. On the other hand, quantitative relaxation contrasts (like the apparent transverse relaxation, R2∗) offer iron and myelin-related contrast, but their dependence on the orientation of microstructure with respect to the applied magnetic field, B0 , is often neglected...
November 3, 2016: NMR in Biomedicine
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