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NMR in Biomedicine

Lauren J O'Donnell, Alessandro Daducci, Demian Wassermann, Christophe Lenglet
Computational methods are crucial for the analysis of diffusion magnetic resonance imaging (MRI) of the brain. Computational diffusion MRI can provide rich information at many size scales, including local microstructure measures such as diffusion anisotropies or apparent axon diameters, whole-brain connectivity information that describes the brain's wiring diagram and population-based studies in health and disease. Many of the diffusion MRI analyses performed today were not possible five, ten or twenty years ago, due to the requirements for large amounts of computer memory or processor time...
November 14, 2017: NMR in Biomedicine
Isabelle Saniour, Gwenaël Gaborit, Anne-Laure Perrier, Laurane Gillette, Guillaume Revillod, Raphaël Sablong, Lionel Duvillaret, Olivier Beuf
During magnetic resonance imaging (MRI) examinations, the average specific absorption rate (SAR) of the whole body is calculated as an index of global energy deposition in biological tissue without taking into account the presence of metallic implants or conductive materials. However, this global SAR calculation is not sufficient to ensure patient safety and a local SAR measurement should be carried out. Several measurement techniques have already been used to evaluate the local SAR, in particular electric field (E-field) probes, but the accuracy of the measurements and the resolutions (spatial and temporal) depend strongly on the measurement method/probe...
November 12, 2017: NMR in Biomedicine
Faezeh Sanaei Nezhad, Adriana Anton, Emilia Michou, JeYoung Jung, Laura M Parkes, Stephen R Williams
γ-Aminobutyric acid (GABA) and glutamate (Glu), major neurotransmitters in the brain, are recycled through glutamine (Gln). All three metabolites can be measured by magnetic resonance spectroscopy in vivo, although GABA measurement at 3 T requires an extra editing acquisition, such as Mescher-Garwood point-resolved spectroscopy (MEGA-PRESS). In a GABA-edited MEGA-PRESS spectrum, Glu and Gln co-edit with GABA, providing the possibility to measure all three in one acquisition. In this study, we investigated the reliability of the composite Glu + Gln (Glx) peak estimation and the possibility of Glu and Gln separation in GABA-edited MEGA-PRESS spectra...
November 12, 2017: NMR in Biomedicine
Harmen Reyngoudt, Suna Turk, Pierre G Carlier
In recent years, quantitative nuclear magnetic resonance imaging and spectroscopy (NMRI and NMRS) have been used more systematically as outcome measures in natural history and clinical trial studies for Duchenne muscular dystrophy (DMD). Whereas most of these studies have emphasized the evaluation of the fat fraction as an assessment for disease severity, less focus has been placed on metabolic indices measured by NMRS. (31) P NMRS in DMD reveals an alkaline inorganic phosphate (Pi ) pool, originating from either leaky dystrophic myocytes or an increased interstitial space...
November 12, 2017: NMR in Biomedicine
Mark Bydder, Gavin Hamilton, Ludovic de Rochefort, Ajinkya Desai, Elhamy R Heba, Rohit Loomba, Jeffrey B Schwimmer, Nikolaus M Szeverenyi, Claude B Sirlin
The purpose of this work was to investigate sources of bias in magnetic resonance imaging (MRI) liver fat quantification that lead to a dependence of the proton density fat fraction (PDFF) on the number of echoes. This was a retrospective analysis of liver MRI data from 463 subjects. The magnitude signal variation with TE from spoiled gradient echo images was curve fitted to estimate the PDFF using a model that included monoexponential R2 * decay and a multi-peak fat spectrum. Additional corrections for non-exponential decay (Gaussian), bi-exponential decay, degree of fat saturation, water frequency shift and noise bias were introduced...
November 12, 2017: NMR in Biomedicine
David J Niles, Jeremy W Gordon, Gengwen Huang, Shannon Reese, Erin B Adamson, Arjang Djamali, Sean B Fain
Hyperpolarized (13) C magnetic resonance imaging (MRI) may be used to non-invasively image the transport and chemical conversion of (13) C-labeled compounds in vivo. In this study, we utilize hyperpolarized (13) C MRI to evaluate metabolic markers in the kidneys longitudinally in a mouse model of partial unilateral ureteral obstruction (pUUO). Partial obstruction was surgically induced in the left ureter of nine adult mice, leaving the right ureter as a control. (1) H and hyperpolarized [1-(13) C]pyruvate MRI of the kidneys was performed 2 days prior to surgery (baseline) and at 3, 7 and 14 days post-surgery...
November 12, 2017: NMR in Biomedicine
Albert P Chen, Angus Z Lau, Yi-Ping Gu, Marie A Schroeder, Jennifer Barry, Charles H Cunningham
Previous studies have demonstrated that using hyperpolarized [2-(13) C]pyruvate as a contrast agent can reveal (13) C signals from metabolites associated with the tricarboxylic acid (TCA) cycle. However, the metabolites detectable from TCA cycle-mediated oxidation of [2-(13) C]pyruvate are the result of several metabolic steps. In the instance of the [5-(13) C]glutamate signal, the amplitude can be modulated by changes to the rates of pyruvate dehydrogenase (PDH) flux, TCA cycle flux and metabolite pool size...
November 6, 2017: NMR in Biomedicine
Renee Miller, Arunark Kolipaka, Martyn P Nash, Alistair A Young
Although magnetic resonance elastography (MRE) has been used to estimate isotropic stiffness in the heart, myocardium is known to have anisotropic properties. This study investigated the determinability of global transversely isotropic material parameters using MRE and finite-element modeling (FEM). A FEM-based material parameter identification method, using a displacement-matching objective function, was evaluated in a gel phantom and simulations of a left ventricular (LV) geometry with a histology-derived fiber field...
November 6, 2017: NMR in Biomedicine
Jia Guo, Zhu Gang, Yanping Sun, Andrew Laine, Scott A Small, Douglas L Rothman
The goals of this study were to develop an acquisition protocol and the analysis tools for Meshcher-Garwood point-resolved spectroscopy (MEGA-PRESS) in mouse brain at 9.4 T, to allow the in vivo detection of γ-aminobutyric acid (GABA) and to examine whether isoflurane alters GABA levels in the thalamus during anesthesia. We implemented the MEGA-PRESS sequence on a Bruker 94/20 system with ParaVision 6.0.1, and magnetic resonance spectra were acquired from nine male wild-type C57BL/6 J mice at the thalamus...
November 3, 2017: NMR in Biomedicine
Brennen J Dobberthien, Anthony G Tessier, Atiyah Yahya
Glutamine (Gln), glutamate (Glu) and γ-aminobutyric acid (GABA) are relevant brain metabolites that can be measured with magnetic resonance spectroscopy (MRS). This work optimizes the point-resolved spectroscopy (PRESS) sequence echo times, TE1 and TE2 , for improved simultaneous quantification of the three metabolites at 9.4 T. Quantification was based on the proton resonances of Gln, Glu and GABA at ≈2.45, ≈2.35 and ≈2.28 ppm, respectively. Glu exhibits overlap with both Gln and GABA; in addition, the Gln peak is contaminated by signal from the strongly coupled protons of N-acetylaspartate (NAA), which resonate at about 2...
November 3, 2017: NMR in Biomedicine
Moritz C Wurnig, Manon Germann, Andreas Boss
The most commonly applied model for the description of diffusion-weighted imaging (DWI) data in perfused organs is bicompartmental intravoxel incoherent motion (IVIM) analysis. In this study, we assessed the ground truth of underlying diffusion components in healthy abdominal organs using an extensive DWI protocol and subsequent computation of apparent diffusion coefficient 'spectra', similar to the computation of previously described T2 relaxation spectra. Diffusion datasets of eight healthy subjects were acquired in a 3-T magnetic resonance scanner using 68 different b values during free breathing (equidistantly placed in the range 0-1005 s/mm(2) )...
November 3, 2017: NMR in Biomedicine
Tianyu Zou, Hao Yu, Chunxiu Jiang, Xianlong Wang, Shanshan Jiang, Qihong Rui, Yingjie Mei, Jinyuan Zhou, Zhibo Wen
The purpose of this work was to investigate the diagnostic performance of amide proton transfer-weighted (APTW) and intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in the preoperative grading of gliomas. Fifty-one patients with suspected gliomas were recruited and underwent a preoperative MRI examination that included APTW and IVIM sequences. All cases were confirmed by postsurgical histopathology. APTW signal intensity, true diffusion coefficient (D), perfusion fraction (f) and pseudo-diffusion coefficient (D*) were applied to assess the solid tumor component and contralateral normal-appearing white matter...
November 3, 2017: NMR in Biomedicine
Georg Oeltzschner, Kimberly L Chan, Muhammad G Saleh, Mark Mikkelsen, Nicolaas A Puts, Richard A E Edden
The primary inhibitory neurotransmitter γ-aminobutyric acid (GABA) and the major antioxidant glutathione (GSH) are compounds of high importance for the function and integrity of the human brain. In this study, a method for simultaneous J-difference spectral-edited magnetic resonance spectroscopy (MRS) of GSH and GABA with suppression of macromolecular (MM) signals at 3 T is proposed. MM-suppressed Hadamard encoding and reconstruction of MEGA (Mescher-Garwood)-edited spectroscopy (HERMES) consists of four sub-experiments (TE = 80 ms), with 20-ms editing pulses applied at: (A) 4...
October 26, 2017: NMR in Biomedicine
Ahmed E Fetit, Jan Novak, Daniel Rodriguez, Dorothee P Auer, Christopher A Clark, Richard G Grundy, Andrew C Peet, Theodoros N Arvanitis
Brain tumours are the most common solid cancers in children in the UK and are the most common cause of cancer deaths in this age group. Despite current advances in MRI, non-invasive diagnosis of paediatric brain tumours has yet to find its way into routine clinical practice. Radiomics, the high-throughput extraction and analysis of quantitative image features (e.g. texture), offers potential solutions for tumour characterization and decision support. In the search for diagnostic oncological markers, the primary aim of this work was to study the application of MRI texture analysis (TA) for the classification of paediatric brain tumours...
October 26, 2017: NMR in Biomedicine
Byeong-Yeul Lee, Xiao-Hong Zhu, Myung Kyun Woo, Gregor Adriany, Scott Schillak, Wei Chen
In vivo (31) P magnetic resonance spectroscopy (MRS) provides a unique tool for the non-invasive study of brain energy metabolism and mitochondrial function. The assessment of bioenergetic impairment in different brain regions is essential to understand the pathophysiology and progression of human brain diseases. This article presents a simple and effective approach which allows the interleaved measurement of (31) P spectra and imaging from two distinct human brain regions of interest with dynamic B0 shimming capability...
October 26, 2017: NMR in Biomedicine
Corinne Balleyguier, Aicha Ben Lakhdar, Ariane Dunant, Marie-Christine Mathieu, Suzette Delaloge, Ralph Sinkus
The purpose of this work was to assess the diagnostic value of magnetic resonance elastography (MRE) in addition to MRI to differentiate malignant from benign breast tumors, and the feasibility of performing MRE on the whole breast. MRE quantified biomechanical properties within the entire breast (50 slices) using an 11 min acquisition protocol at an isotropic image acquisition resolution of 2 × 2 × 2 mm(3) . Fifty patients were included. Finally, 43 patients (median age 52) with a suspect breast lesion detected by mammography and/or ultrasound were examined by MRI and MRE at 1...
October 26, 2017: NMR in Biomedicine
Yonathan T Araya, Francisco Martínez-Santiesteban, William B Handler, Chad T Harris, Blaine A Chronik, Timothy J Scholl
This study quantified the spin-lattice relaxation rate (R1 ) dispersion of murine tissues from 0.24 mT to 3 T. A combination of ex vivo and in vivo spin-lattice relaxation rate measurements were acquired for murine tissue. Selected brain, liver, kidney, muscle, and fat tissues were excised and R1 dispersion profiles were acquired from 0.24 mT to 1.0 T at 37 °C, using a fast field-cycling MR (FFC-MR) relaxometer. In vivo R1 dispersion profiles of mice were acquired from 1.26 T to 1.74 T at 37 °C, using FFC-MRI on a 1...
October 18, 2017: NMR in Biomedicine
Mark Chiew, Wenwen Jiang, Brian Burns, Peder Larson, Adam Steel, Peter Jezzard, M Albert Thomas, Uzay E Emir
It has been shown that density-weighted (DW) k-space sampling with spiral and conventional phase encoding trajectories reduces spatial side lobes in magnetic resonance spectroscopic imaging (MRSI). In this study, we propose a new concentric ring trajectory (CRT) for DW-MRSI that samples k-space with a density that is proportional to a spatial, isotropic Hanning window. The properties of two different DW-CRTs were compared against a radially equidistant (RE) CRT and an echo-planar spectroscopic imaging (EPSI) trajectory in simulations, phantoms and in vivo experiments...
October 18, 2017: NMR in Biomedicine
Abubakr Eldirdiri, Andreas Clemmensen, Sean Bowen, Andreas Kjaer, Jan Henrik Ardenkjaer-Larsen
A co-polarization scheme for [1,4-(13) C2 ]fumarate and [1-(13) C]pyruvate is presented to simultaneously assess necrosis and metabolism in rats with hyperpolarized (13) C magnetic resonance (MR). The co-polarization was performed in a SPINlab polarizer. In addition, the feasibility of simultaneous positron emission tomography (PET) and MR of small animals with a clinical PET/MR scanner is demonstrated. The hyperpolarized metabolic MR and PET was demonstrated in a rat model of necrosis. The polarization and T1 of the co-polarized [1,4-(13) C2 ]fumarate and [1-(13) C]pyruvate substrates were measured in vitro and compared with those obtained when the substrates were polarized individually...
October 18, 2017: NMR in Biomedicine
U Eliav, G Navon
In T1 weighted magnetic resonance imaging of brain and spinal cord in the clinical setting, the white matter (WM) appears with greater intensity than the gray matter (GM). This contrast has been assigned to differences in T1 values. In these experiments the RF pulses are too long to excite both the water and the species with restricted motion of the protons (SRMP). In in vitro studies using short RF pulses, the contrast is reversed, with greater intensity for the GM. These results raise the question of whether magnetization transfer (MT) plays a role in the contrast observed in the T1 weighting experiments...
October 18, 2017: NMR in Biomedicine
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