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NMR in Biomedicine

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https://www.readbyqxmd.com/read/28915341/-31-p-magnetic-resonance-fingerprinting-for-rapid-quantification-of-creatine-kinase-reaction-rate-in-vivo
#1
Charlie Y Wang, Yuchi Liu, Shuying Huang, Mark A Griswold, Nicole Seiberlich, Xin Yu
The purpose of this work was to develop a (31) P spectroscopic magnetic resonance fingerprinting (MRF) method for fast quantification of the chemical exchange rate between phosphocreatine (PCr) and adenosine triphosphate (ATP) via creatine kinase (CK). A (31) P MRF sequence (CK-MRF) was developed to quantify the forward rate constant of ATP synthesis via CK ( kfCK), the T1 relaxation time of PCr ( T1PCr), and the PCr-to-ATP concentration ratio ( MRPCr). The CK-MRF sequence used a balanced steady-state free precession (bSSFP)-type excitation with ramped flip angles and a unique saturation scheme sensitive to the exchange between PCr and γATP...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28915340/metabolic-profile-of-visual-cortex-in-diabetic-rats-measured-with-in-vivo-proton-mrs
#2
Shuang Li, Xinghua Wang, Junjie Yang, Hao Lei, Xuxia Wang, Yi Xiang
The purpose of the present study was to characterize the metabolic profile of the visual cortex in streptozotocin-induced Type 1 diabetic rats by means of in vivo proton MRS. Several metabolite concentration ratios in the visual cortex were calculated. In addition, postmortem histologic analyses for retinal ganglion cell (RGC) loss, optic nerve injury and visual cortex alterations were monitored. The results showed that diabetes induced several changes in visual cortex metabolites, such as reduced N-acetylaspartate, glutamate, γ-aminobutyric acid, taurine and choline-containing compound levels...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28915319/an-improved-model-for-prostate-diffusion-incorporating-the-results-of-monte-carlo-simulations-of-diffusion-in-the-cellular-compartment
#3
Nima Gilani, Paul Malcolm, Glyn Johnson
The purpose of this work was to refine a previously published model of prostate diffusion by incorporating improved estimates of cellular diffusivity obtained by Monte Carlo simulation. Stromal and epithelial cell size and intracellular volume fraction in different grades of cancer were determined from histological images. Diffusion in different mixtures of cells, corresponding to different tumor grades, was simulated and cellular apparent diffusion coefficient and kurtosis values determined. These values were incorporated into the previously published model of prostate diffusion and model predictions compared with values found in the literature...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28915318/applications-of-high-resolution-magic-angle-spinning-mrs-in-biomedical-studies-ii-human-diseases
#4
REVIEW
Christopher Dietz, Felix Ehret, Francesco Palmas, Lindsey A Vandergrift, Yanni Jiang, Vanessa Schmitt, Vera Dufner, Piet Habbel, Johannes Nowak, Leo L Cheng
High-resolution magic angle spinning (HRMAS) MRS is a powerful method for gaining insight into the physiological and pathological processes of cellular metabolism. Given its ability to obtain high-resolution spectra of non-liquid biological samples, while preserving tissue architecture for subsequent histopathological analysis, the technique has become invaluable for biochemical and biomedical studies. Using HRMAS MRS, alterations in measured metabolites, metabolic ratios, and metabolomic profiles present the possibility to improve identification and prognostication of various diseases and decipher the metabolomic impact of drug therapies...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28915314/-1-h-mrs-processing-parameters-affect-metabolite-quantification-the-urgent-need-for-uniform-and-transparent-standardization
#5
Alex A Bhogal, Remmelt R Schür, Lotte C Houtepen, Bart van de Bank, Vincent O Boer, Anouk Marsman, Peter B Barker, Tom W J Scheenen, Jannie P Wijnen, Christiaan H Vinkers, Dennis W J Klomp
Proton magnetic resonance spectroscopy ((1) H-MRS) can be used to quantify in vivo metabolite levels, such as lactate, γ-aminobutyric acid (GABA) and glutamate (Glu). However, there are considerable analysis choices which can alter the accuracy or precision of (1) H-MRS metabolite quantification. It is currently unknown to what extent variations in the analysis pipeline used to quantify (1) H-MRS data affect outcomes. The purpose of this study was to evaluate whether the quantification of identical (1) H-MRS scans across independent and experienced research groups would yield comparable results...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28915312/dce-and-dw-mri-as-early-imaging-biomarkers-of-treatment-response-in-a-preclinical-model-of-triple-negative-breast-cancer
#6
Stephanie L Barnes, Anna G Sorace, Jennifer G Whisenant, J Oliver McIntyre, Hakmook Kang, Thomas E Yankeelov
This work evaluates quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted MRI (DW-MRI) parameters as early biomarkers of response in a preclinical model of triple negative breast cancer (TNBC). The standard Tofts' model of DCE-MRI returns estimates of the volume transfer constant (K(trans) ) and the extravascular extracellular volume fraction (ve ). DW-MRI returns estimates of the apparent diffusion coefficient (ADC). Mice (n = 38) were injected subcutaneously with MDA-MB-231...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28915311/can-increased-spatial-resolution-solve-the-crossing-fiber-problem-for-diffusion-mri
#7
Kurt Schilling, Yurui Gao, Vaibhav Janve, Iwona Stepniewska, Bennett A Landman, Adam W Anderson
It is now widely recognized that voxels with crossing fibers or complex geometrical configurations present a challenge for diffusion MRI (dMRI) reconstruction and fiber tracking, as well as microstructural modeling of brain tissues. This "crossing fiber" problem has been estimated to affect anywhere from 30% to as many as 90% of white matter voxels, and it is often assumed that increasing spatial resolution will decrease the prevalence of voxels containing multiple fiber populations. The aim of this study is to estimate the extent of the crossing fiber problem as we progressively increase the spatial resolution, with the goal of determining whether it is possible to mitigate this problem with higher resolution spatial sampling...
September 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28902423/partitioning-k-space-for-cylindrical-three-dimensional-rapid-acquisition-with-relaxation-enhancement-imaging-in-the-mouse-brain
#8
T Leigh Spencer Noakes, R Mark Henkelman, Brian J Nieman
Three-dimensional rapid acquisition with relaxation enhancement (RARE) scans require the assignment of each phase encode step in two dimensions to an echo in the echo train. Although this assignment is frequently made across the entire Cartesian grid, collection of only the central cylinder of k-space by eliminating the corners in each phase encode dimension reduces the scan time by ~22% with negligible impact on image quality. The recipe for the assignment of echoes to grid points for such an acquisition is less straightforward than for the simple full Cartesian acquisition case, and has important implications for image quality...
September 13, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28902421/the-impact-of-white-matter-fiber-orientation-in-single-acquisition-quantitative-susceptibility-mapping
#9
Marta Lancione, Michela Tosetti, Graziella Donatelli, Mirco Cosottini, Mauro Costagli
The aim of this work was to assess the impact of tissue structural orientation on quantitative susceptibility mapping (QSM) reliability, and to provide a criterion to identify voxels in which measures of magnetic susceptibility (χ) are most affected by spatial orientation effects. Four healthy volunteers underwent 7-T magnetic resonance imaging (MRI). Multi-echo, gradient-echo sequences were used to obtain quantitative maps of frequency shift (FS) and χ. Information from diffusion tensor imaging (DTI) was used to investigate the relationship between tissue orientation and FS measures and QSM...
September 13, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28886240/a-review-of-diffusion-mri-of-typical-white-matter-development-from-early-childhood-to-young-adulthood
#10
Catherine Lebel, Sarah Treit, Christian Beaulieu
Understanding typical, healthy brain development provides a baseline from which to detect and characterize brain anomalies associated with various neurological or psychiatric disorders and diseases. Diffusion MRI is well suited to study white matter development, as it can virtually extract individual tracts and yield parameters that may reflect alterations in the underlying neural micro-structure (e.g. myelination, axon density, fiber coherence), though it is limited by its lack of specificity and other methodological concerns...
September 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28885746/pseudo-extravasation-rate-constant-of-dynamic-susceptibility-contrast-mri-determined-from-pharmacokinetic-first-principles
#11
Xin Li, Csanad G Varallyay, Seymur Gahramanov, Rongwei Fu, William D Rooney, Edward A Neuwelt
Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) is widely used to obtain informative perfusion imaging biomarkers, such as the relative cerebral blood volume (rCBV). The related post-processing software packages for DSC-MRI are available from major MRI instrument manufacturers and third-party vendors. One unique aspect of DSC-MRI with low-molecular-weight gadolinium (Gd)-based contrast reagent (CR) is that CR molecules leak into the interstitium space and therefore confound the DSC signal detected...
September 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28885745/intravoxel-incoherent-motion-mri-as-a-means-to-measure-in-vivo-perfusion-a-review-of-the-evidence
#12
REVIEW
Christian Federau
The idea that in vivo intravoxel incoherent motion magnetic resonance signal is influenced by blood motion in the microvasculature is exciting, because it suggests that local and quantitative perfusion information can be obtained in a simple and elegant way from a few diffusion-weighted images, without contrast injection. When the method was proposed in the late 1980s some doubts appeared as to its feasibility, and, probably because the signal to noise and image quality at the time was not sufficient, no obvious experimental evidence could be produced to alleviate them...
September 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28885742/adaptive-bulk-motion-exclusion-for-improved-robustness-of-abdominal-magnetic-resonance-imaging
#13
Bjorn Stemkens, Thomas Benkert, Hersh Chandarana, Mark E Bittman, Cornelis A T Van den Berg, Jan J W Lagendijk, Daniel K Sodickson, Rob H N Tijssen, Kai Tobias Block
Non-Cartesian magnetic resonance imaging (MRI) sequences have shown great promise for abdominal examination during free breathing, but break down in the presence of bulk patient motion (i.e. voluntary or involuntary patient movement resulting in translation, rotation or elastic deformations of the body). This work describes a data-consistency-driven image stabilization technique that detects and excludes bulk movements during data acquisition. Bulk motion is identified from changes in the signal intensity distribution across different elements of a multi-channel receive coil array...
September 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28873255/accelerated-4d-self-gated-mri-of-tibiofemoral-kinematics
#14
Valentina Mazzoli, Jasper Schoormans, Martijn Froeling, Andre M Sprengers, Bram F Coolen, Nico Verdonschot, Gustav J Strijkers, Aart J Nederveen
Anatomical (static) magnetic resonance imaging (MRI) is the most useful imaging technique for the evaluation and assessment of internal derangement of the knee, but does not provide dynamic information and does not allow the study of the interaction of the different tissues during motion. As knee pain is often only experienced during dynamic tasks, the ability to obtain four-dimensional (4D) images of the knee during motion could improve the diagnosis and provide a deeper understanding of the knee joint. In this work, we present a novel approach for dynamic, high-resolution, 4D imaging of the freely moving knee without the need for external triggering...
September 5, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28858413/decoding-the-microstructural-correlate-of-diffusion-mri
#15
Svenja Caspers, Markus Axer
Diffusion imaging has evolved considerably over the past decade. While it provides valuable information about the structural connectivity at the macro- and mesoscopic scale, bridging the gap to the microstructure at the level of single nerve fibers poses an enormous challenge. This is particularly true for the human brain with its large size, its large white-matter volume and availability of histological techniques for studying human whole-brain sections and subsequent 3D reconstruction. Classic post-mortem techniques for studying the fiber architecture of the brain, such as myeloarchitectonic staining or dye tracing, are complemented by novel histological approaches, such as 3D polarized light imaging or optical coherence tomography, enabling unique insight into the fiber architecture from large fiber bundles within deep white matter to single nerve fibers in the cortex...
August 31, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28857310/orotracheal-manganese-enhanced-mri-memri-an-effective-approach-for-lung-tumor-detection
#16
Andrea Bianchi, Oliviero L Gobbo, Sandrine Dufort, Lucie Sancey, François Lux, Olivier Tillement, Jean-Luc Coll, Yannick Crémillieux
Lung cancer is a primary cause of cancer deaths worldwide. Timely detection of this pathology is necessary to delay or interrupt lung cancer progression, ultimately resulting in a possible better prognosis for the patient. In this context, magnetic resonance imaging (MRI) is especially promising. Ultra-short echo time (UTE) MRI sequences, in combination with gadolinium-based contrast agents, have indeed shown to be especially adapted to the detection of lung neoplastic lesions at submillimeter precision. Manganese-enhanced MRI (MEMRI) increasingly appears to be a possible effective alternative to gadolinium-enhanced MRI...
August 31, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28841762/comparison-of-different-compressed-sensing-algorithms-for-low-snr-19-f-mri-applications-imaging-of-transplanted-pancreatic-islets-and-cells-labeled-with-perfluorocarbons
#17
Sayuan Liang, Tom Dresselaers, Karim Louchami, Ce Zhu, Yipeng Liu, Uwe Himmelreich
Transplantation of pancreatic islets is a possible treatment option for patients suffering from Type I diabetes. In vivo imaging of transplanted islets is important for assessment of the transplantation site and islet distribution. Thanks to its high specificity, the absence of intrinsic background signal in tissue and its potential for quantification, (19) F MRI is a promising technique for monitoring the fate of transplanted islets in vivo. In order to overcome the inherent low sensitivity of (19) F MRI, leading to long acquisition times with low signal-to-noise ratio (SNR), compressed sensing (CS) techniques are a valuable option...
August 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28841761/user-independent-diffusion-tensor-imaging-analysis-pipelines-in-a-rat-model-presenting-ventriculomegalia-a-comparison-study
#18
Luis Akakpo, Wyston C Pierre, Chen Jin, Irène Londono, Philippe Pouliot, Gregory A Lodygensky
Automated analysis of diffusion tensor imaging (DTI) data is an appealing way to process large datasets in an unbiased manner. However, automation can sometimes be linked to a lack of interpretability. Two whole-brain, automated and voxelwise methods exist: voxel-based analysis (VBA) and tract-based spatial statistics (TBSS). In VBA, the amount of smoothing has been shown to influence the results. TBSS is free of this step, but a projection procedure is introduced to correct for residual misalignments. This projection assigns the local highest fractional anisotropy (FA) value to the mean FA skeleton, which represents white matter tract centers...
August 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28841758/precision-and-accuracy-of-diffusion-kurtosis-estimation-and-the-influence-of-b-value-selection
#19
Andrey Chuhutin, Brian Hansen, Sune Nørhøj Jespersen
Diffusion kurtosis imaging (DKI) is an extension of diffusion tensor imaging that accounts for leading non-Gaussian diffusion effects. In DKI studies, a wide range of different gradient strengths (b-values) is used, which is known to affect the estimated diffusivity and kurtosis parameters. Hence there is a need to assess the accuracy and precision of the estimated parameters as a function of b-value. This work examines the error in the estimation of mean of the kurtosis tensor (MKT) with respect to the ground truth, using simulations based on a biophysical model for both gray (GM) and white (WM) matter...
August 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28805936/characterizing-hypoxia-in-human-glioma-a-simultaneous-multimodal-mri-and-pet-study
#20
Christine Preibisch, Kuangyu Shi, Anne Kluge, Mathias Lukas, Benedikt Wiestler, Jens Göttler, Jens Gempt, Florian Ringel, Mohamed Al Jaberi, Jürgen Schlegel, Bernhard Meyer, Claus Zimmer, Thomas Pyka, Stefan Förster
Hypoxia plays an important role for the prognosis and therapy response of cancer. Thus, hypoxia imaging would be a valuable tool for pre-therapeutic assessment of tumor malignancy. However, there is no standard validated technique for clinical application available yet. Therefore, we performed a study in 12 patients with high-grade glioma, where we directly compared the two currently most promising techniques, namely the MR-based relative oxygen extraction fraction (MR-rOEF) and the PET hypoxia marker H-1-(3-[(18) F]-fluoro-2-hydroxypropyl)-2-nitroimidazole ([(18) F]-FMISO)...
August 14, 2017: NMR in Biomedicine
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