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https://www.readbyqxmd.com/read/28338046/solitary-perturbations-in-the-steep-boundary-of-magnetized-toroidal-plasma
#1
J E Lee, G S Yun, W Lee, M H Kim, M Choi, J Lee, M Kim, H K Park, J G Bak, W H Ko, Y S Park
Solitary perturbations (SPs) localized both poloidally and radially are detected within ~100 μs before the partial collapse of the high pressure gradient boundary region (called pedestal) of magnetized toroidal plasma in the KSTAR tokamak device. The SP develops with a low toroidal mode number (typically unity) in the pedestal ingrained with quasi-stable edge-localized mode (QSM) which commonly appears during the inter-collapse period. The SPs have smaller mode pitch and different (often opposite) rotation velocity compared to the QSMs...
March 24, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28295954/clinical-quantitative-susceptibility-mapping-qsm-biometal-imaging-and-its-emerging-roles-in-patient-care
#2
REVIEW
Yi Wang, Pascal Spincemaille, Zhe Liu, Alexey Dimov, Kofi Deh, Jianqi Li, Yan Zhang, Yihao Yao, Kelly M Gillen, Alan H Wilman, Ajay Gupta, Apostolos John Tsiouris, Ilhami Kovanlikaya, Gloria Chia-Yi Chiang, Jonathan W Weinsaft, Lawrence Tanenbaum, Weiwei Chen, Wenzhen Zhu, Shixin Chang, Min Lou, Brian H Kopell, Michael G Kaplitt, David Devos, Toshinori Hirai, Xuemei Huang, Yukunori Korogi, Alexander Shtilbans, Geon-Ho Jahng, Daniel Pelletier, Susan A Gauthier, David Pitt, Ashley I Bush, Gary M Brittenham, Martin R Prince
Quantitative susceptibility mapping (QSM) has enabled magnetic resonance imaging (MRI) of tissue magnetic susceptibility to advance from simple qualitative detection of hypointense blooming artifacts to precise quantitative measurement of spatial biodistributions. QSM technology may be regarded to be sufficiently developed and validated to warrant wide dissemination for clinical applications of imaging isotropic susceptibility, which is dominated by metals in tissue, including iron and calcium. These biometals are highly regulated as vital participants in normal cellular biochemistry, and their dysregulations are manifested in a variety of pathologic processes...
March 10, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28295523/quantitative-susceptibility-mapping-based-cerebral-metabolic-rate-of-oxygen-mapping-with-minimum-local-variance
#3
Jingwei Zhang, Junghun Cho, Dong Zhou, Thanh D Nguyen, Pascal Spincemaille, Ajay Gupta, Yi Wang
PURPOSE: The objective of this study was to demonstrate the feasibility of a cerebral metabolic rate of oxygen (CMRO2 ) mapping method based on its minimum local variance (MLV) without vascular challenge using quantitative susceptibility mapping (QSM) and cerebral blood flow (CBF). METHODS: Three-dimensional multi-echo gradient echo imaging and arterial spin labeling were performed in 11 healthy subjects to calculate QSM and CBF. Minimum local variance was used to compute whole-brain CMRO2 map from QSM and CBF...
March 10, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28289372/improved-quantification-of-cerebral-vein-oxygenation-using-partial-volume-correction
#4
Phillip G D Ward, Audrey P Fan, Parnesh Raniga, David G Barnes, David L Dowe, Amanda C L Ng, Gary F Egan
Purpose: Quantitative susceptibility mapping (QSM) enables cerebral venous characterization and physiological measurements, such as oxygen extraction fraction (OEF). The exquisite sensitivity of QSM to deoxygenated blood makes it possible to image small veins; however partial volume effects must be addressed for accurate quantification. We present a new method, Iterative Cylindrical Fitting (ICF), to estimate voxel-based partial volume effects for susceptibility maps and use it to improve OEF quantification of small veins with diameters between 1...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/28263417/methods-for-the-computation-of-templates-from-quantitative-magnetic-susceptibility-maps-qsm-toward-improved-atlas-and-voxel-based-analyses-vba
#5
Jannis Hanspach, Michael G Dwyer, Niels P Bergsland, Xiang Feng, Jesper Hagemeier, Nicola Bertolino, Paul Polak, Jürgen R Reichenbach, Robert Zivadinov, Ferdinand Schweser
PURPOSE: To develop and assess a method for the creation of templates for voxel-based analysis (VBA) and atlas-based approaches using quantitative magnetic susceptibility mapping (QSM). MATERIALS AND METHODS: We studied four strategies for the creation of magnetic susceptibility brain templates, derived as successive extensions of the conventional template generation (CONV) based on only T1 -weighted (T1 w) images. One method that used only T1 w images involved a minor improvement of CONV (U-CONV)...
March 6, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28261863/bone-quantitative-susceptibility-mapping-using-a-chemical-species-specific-r2-signal-model-with-ultrashort-and-conventional-echo-data
#6
Alexey V Dimov, Zhe Liu, Pascal Spincemaille, Martin R Prince, Jiang Du, Yi Wang
PURPOSE: To develop quantitative susceptibility mapping (QSM) of bone using an ultrashort echo time (UTE) gradient echo (GRE) sequence for signal acquisition and a bone-specific effective transverse relaxation rate ( R2*) to model water-fat MR signals for field mapping. METHODS: Three-dimensional radial UTE data (echo times ≥ 40 μs) was acquired on a 3 Tesla scanner and fitted with a bone-specific signal model to map the chemical species and susceptibility field...
March 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28251685/primal-dual-and-forward-gradient-implementation-for-quantitative-susceptibility-mapping
#7
Youngwook Kee, Kofi Deh, Alexey Dimov, Pascal Spincemaille, Yi Wang
PURPOSE: To investigate the computational aspects of the prior term in quantitative susceptibility mapping (QSM) by (i) comparing the Gauss-Newton conjugate gradient (GNCG) algorithm that uses numerical conditioning (ie, modifies the prior term) with a primal-dual (PD) formulation that avoids this, and (ii) carrying out a comparison between a central and forward difference scheme for the discretization of the prior term. THEORY AND METHODS: A spatially continuous formulation of the regularized QSM inversion problem and its PD formulation were derived...
March 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28188873/an-improved-fsl-first-pipeline-for-subcortical-gray-matter-segmentation-to-study-abnormal-brain-anatomy-using-quantitative-susceptibility-mapping-qsm
#8
Xiang Feng, Andreas Deistung, Michael G Dwyer, Jesper Hagemeier, Paul Polak, Jessica Lebenberg, Frédérique Frouin, Robert Zivadinov, Jürgen R Reichenbach, Ferdinand Schweser
Accurate and robust segmentation of subcortical gray matter (SGM) nuclei is required in many neuroimaging applications. FMRIB's Integrated Registration and Segmentation Tool (FIRST) is one of the most popular software tools for automated subcortical segmentation based on T1-weighted (T1w) images. In this work, we demonstrate that FIRST tends to produce inaccurate SGM segmentation results in the case of abnormal brain anatomy, such as present in atrophied brains, due to a poor spatial match of the subcortical structures with the training data in the MNI space as well as due to insufficient contrast of SGM structures on T1w images...
February 7, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28168364/effects-of-aging-on-formula-see-text-formula-see-text-and-qsm-mri-values-in-the-subcortex
#9
M C Keuken, P-L Bazin, K Backhouse, S Beekhuizen, L Himmer, A Kandola, J J Lafeber, L Prochazkova, A Trutti, A Schäfer, R Turner, B U Forstmann
The aging brain undergoes several anatomical changes that can be measured with Magnetic Resonance Imaging (MRI). Early studies using lower field strengths have assessed changes in tissue properties mainly qualitatively, using [Formula: see text]- or [Formula: see text]- weighted images to provide image contrast. With the development of higher field strengths (7 T and above) and more advanced MRI contrasts, quantitative measures can be acquired even of small subcortical structures. This study investigates volumetric, spatial, and quantitative MRI parameter changes associated with healthy aging in a range of subcortical nuclei, including the basal ganglia, red nucleus, and the periaqueductal grey...
February 6, 2017: Brain Structure & Function
https://www.readbyqxmd.com/read/28126551/exploring-the-origins-of-echo-time-dependent-quantitative-susceptibility-mapping-qsm-measurements-in-healthy-tissue-and-cerebral-microbleeds
#10
Matthew J Cronin, Nian Wang, Kyle S Decker, Hongjiang Wei, Wen-Zhen Zhu, Chunlei Liu
Quantitative susceptibility mapping (QSM) is increasingly used to measure variation in tissue composition both in the brain and in other areas of the body in a range of disease pathologies. Although QSM measurements were originally believed to be independent of the echo time (TE) used in the gradient-recalled echo (GRE) acquisition from which they are derived; recent literature (Sood et al., 2016) has shown that these measurements can be highly TE-dependent in a number of brain regions. In this work we systematically investigate possible causes of this effect through analysis of apparent frequency and QSM measurements derived from data acquired at multiple TEs in vivo in healthy brain regions and in cerebral microbleeds (CMBs); QSM data acquired in a gadolinium-doped phantom; and in QSM data derived from idealized simulated phase data...
January 23, 2017: NeuroImage
https://www.readbyqxmd.com/read/28113841/quantitative-susceptibility-mapping-using-structural-feature-based-collaborative-reconstruction-sfcr-in-the-human-brain
#11
Lijun Bao, Xu Li, Congbo Cai, Zhong Chen, Peter van Zijl
The reconstruction of MR quantitative susceptibility mapping (QSM) from local phase measurements is an ill posed inverse problem and different regularization strategies incorporating a priori information extracted from magnitude and phase images have been proposed. However, the anatomy observed in magnitude and phase images does not always coincide spatially with that in susceptibility maps, which could give erroneous estimation in the reconstructed susceptibility map. In this paper, we develop a structural feature based collaborative reconstruction (SFCR) method for QSM including both magnitude and susceptibility based information...
March 22, 2016: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28113561/implementing-nonlinear-feedback-controllers-using-dna-strand-displacement-reactions
#12
Rucha Sawlekar, Francesco Montefusco, Vishwesh V Kulkarni, Declan G Bates
We show how an important class of nonlinear feedback controllers can be designed using idealized abstract chemical reactions and implemented via DNA strand displacement (DSD) reactions. Exploiting chemical reaction networks (CRNs) as a programming language for the design of complex circuits and networks, we show how a set of unimolecular and bimolecular reactions can be used to realize input-output dynamics that produce a nonlinear quasi sliding mode (QSM) feedback controller. The kinetics of the required chemical reactions can then be implemented as enzyme-free, enthalpy/entropy driven DNA reactions using a toehold mediated strand displacement mechanism via Watson-Crick base pairing and branch migration...
April 29, 2016: IEEE Transactions on Nanobioscience
https://www.readbyqxmd.com/read/28097689/investigating-magnetic-susceptibility-of-human-knee-joint-at-7-tesla
#13
Hongjiang Wei, Russell Dibb, Kyle Decker, Nian Wang, Yuyao Zhang, Xiaopeng Zong, Weili Lin, Daniel B Nissman, Chunlei Liu
PURPOSE: To evaluate the magnetic susceptibility properties of different anatomical structures within the knee joint using quantitative susceptibility mapping (QSM). METHODS: A collagen tissue model was simulated and ex vivo animal cartilage experiments were conducted at 9.4 Tesla (T) to evaluate the B0 orientation-dependent magnetic susceptibility contrast observed in cartilage. Furthermore, nine volunteers (six healthy subjects without knee pain history and three patients with known knee injury, between 29 and 58 years old) were scanned using gradient-echo acquisitions on a high-field 7T MR scanner...
January 17, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28065850/deep-grey-matter-iron-accumulation-in-alcohol-use-disorder
#14
Michal Juhás, Hongfu Sun, Matthew R G Brown, Marnie B MacKay, Karl F Mann, Wolfgang H Sommer, Alan H Wilman, Serdar M Dursun, Andrew J Greenshaw
PURPOSE: Evaluate brain iron accumulation in alcohol use disorder (AUD) patients compared to controls using quantitative susceptibility mapping (QSM). METHODS: QSM was performed retrospectively by using phase images from resting state functional magnetic resonance imaging (fMRI). 20 male AUD patients and 15 matched healthy controls were examined. Susceptibility values were manually traced in deep grey matter regions including caudate nucleus, combined putamen and globus pallidus, combined substantia nigra and red nucleus, dentate nucleus, and a reference white matter region in the internal capsule...
January 5, 2017: NeuroImage
https://www.readbyqxmd.com/read/28046752/su-f-i-24-feasibility-of-magnetic-susceptibility-to-relative-electron-density-conversion-method-for-radiation-therapy
#15
K Ito, N Kadoya, M Chiba, K Sato, T Nagasaka, K Yamanaka, S Dobashi, K Takeda, H Matsushita, K Jingu
PURPOSE: The aim of this study is to develop radiation treatment planning using magnetic susceptibility obtained from quantitative susceptibility mapping (QSM) via MR imaging. This study demonstrates the feasibility of a method for generating a substitute for a CT image from an MRI. METHODS: The head of a healthy volunteer was scanned using a CT scanner and a 3.0 T MRI scanner. The CT imaging was performed with a slice thickness of 2.5 mm at 80 and 120 kV (dual-energy scan)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046245/su-d-207a-04-use-of-gradient-echo-plural-contrast-imaging-gepci-in-mr-guided-radiation-therapy-a-feasibility-study-targeting-brain-treatment
#16
B Cai, J Wen, Y Rao, C Tsien, J Huang, O Green, S Mutic, D Yablonskiy, H Gach
PURPOSE: To implement the Gradient Echo Plural Contrast Imaging(GEPCI) technique in MRI-simulation for radiation therapy and assess the feasibility of using GEPCI images with advanced inhomogeneity correction in MRI-guided radiotherapy for brain treatment. METHODS: An optimized multigradient-echo GRE sequence (TR=50ms;TE1=4ms;delta_TE=4ms;flip angle=300,11 Echoes) was developed to generate both structural (T1w and T2*w) and functional MRIs (field and susceptibility maps) from a single acquisition...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/27995062/magnetic-susceptibility-in-the-deep-layers-of-the-primary-motor-cortex-in-amyotrophic-lateral-sclerosis
#17
M Costagli, G Donatelli, L Biagi, E Caldarazzo Ienco, G Siciliano, M Tosetti, M Cosottini
Amyotrophic Lateral Sclerosis (ALS) is a progressive neurological disorder that entails degeneration of both upper and lower motor neurons. The primary motor cortex (M1) in patients with upper motor neuron (UMN) impairment is pronouncedly hypointense in Magnetic Resonance (MR) T2* contrast. In the present study, 3D gradient-recalled multi-echo sequences were used on a 7 Tesla MR system to acquire T2*-weighted images targeting M1 at high spatial resolution. MR raw data were used for Quantitative Susceptibility Mapping (QSM)...
2016: NeuroImage: Clinical
https://www.readbyqxmd.com/read/27987234/deciphering-fungal-dimorphism-farnesol-s-unanswered-questions
#18
Kenneth W Nickerson, Audrey L Atkin
Candida albicans excretes E,E-farnesol as a virulence factor and quorum sensing molecule that prevents the yeast to hyphal conversion. Polke et al. (2016) identified eed1Δ/Δ as the first farnesol hypersensitive mutant of C. albicans. eed1Δ/Δ also excretes 10X more farnesol and while able to form hyphae, it cannot maintain hyphae. This mutant enables new research into unanswered questions, including the existence of potential farnesol receptors and transporters, regulation of farnesol synthesis, and relationships among farnesol, germ tube formation and hyphal maintenance...
December 17, 2016: Molecular Microbiology
https://www.readbyqxmd.com/read/27986608/changes-in-brain-iron-concentration-after-exposure-to-high-altitude-hypoxia-measured-by-quantitative-susceptibility-mapping
#19
Lin Chen, Congbo Cai, Tianhe Yang, Jianzhong Lin, Shuhui Cai, Jiaxing Zhang, Zhong Chen
Hypoxia can induce physiological changes. This study aims to explore effects of high-altitude (HA) hypoxia on cerebral iron concentration. Twenty-nine healthy sea-level participants were tested shortly before and after approximately 4-week adaptation to the HA environment at fQinghai-Tibet Plateau (4200m), and were re-investigated after re-adaptation to the sea-level environment one year later. Iron concentration was quantified with quantitative susceptibility mapping (QSM), and the results were compared with transverse relaxation rate (R(*)2) measurements...
February 15, 2017: NeuroImage
https://www.readbyqxmd.com/read/27939794/studying-cyto-and-myeloarchitecture-of-the-human-cortex-at-ultra-high-field-with-quantitative-imaging-r1-r2-and-magnetic-susceptibility
#20
José P Marques, Diana Khabipova, Rolf Gruetter
In this manuscript, the use of quantitative imaging at ultra-high field is evaluated as a mean to study cyto and myelo-architecture of the cortex. The quantitative contrasts used are the longitudinal relaxation rate (R1), apparent transverse relaxation rate (R2(*)) and quantitative susceptibility mapping (QSM). The quantitative contrasts were computed using high resolution in-vivo (0.65mm isotropic) brain data acquired at 7T. The performance of the different quantitative approaches was evaluated by visualizing the contrast between known highly myelinated primary sensory cortex regions and the neighbouring cortex...
February 15, 2017: NeuroImage
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