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Benjamín Garzón, Rouslan Sitnikov, Lars Bäckman, Grégoria Kalpouzos
Alterations in iron concentration in certain deep gray matter regions are known to occur in aging and several clinical conditions. In vivo measurements of R2(∗) transverse relaxation rates and quantitative susceptibility mapping (QSM) have been shown to be strongly correlated with iron concentration in tissue, but their calculation requires the acquisition of a multi-echo gradient recalled echo sequence (MGRE). In the current study, we examined the feasibility of approximating R2(∗) rates using metrics derived from fMRI-EPI and T2-weighted FLAIR images, which are widely available...
April 21, 2017: Magnetic Resonance Imaging
Berkin Bilgic, Huihui Ye, Lawrence L Wald, Kawin Setsompop
T2⁎ weighted 3D Gradient Echo (GRE) acquisition is the main sequence used for Susceptibility Weighted Imaging (SWI) and Quantitative Susceptibility Mapping (QSM). These applications require a long echo time (TE) to build up phase contrast, requiring a long repetition time (TR), and leading to excessively lengthy scans. The long TE acquisition creates a significant amount of unused time within each TR, which can be utilized for either multi-echo sampling or additional image encoding with the echo-shift technique...
April 20, 2017: NeuroImage
Yawen Sun, Xin Ge, Xu Han, Wenwei Cao, Yao Wang, Weina Ding, Mengqiu Cao, Yong Zhang, Qun Xu, Yan Zhou, Jianrong Xu
The presence and pattern of iron accumulation in subcortical vascular mild cognitive impairment (svMCI) and their effects on cognition have rarely been investigated. We aimed to examine brain iron deposition in svMCI subjects using quantitative susceptibility mapping (QSM). Moreover, we aimed to investigate the correlation between brain iron deposition and the severity of cognitive impairment as indicated by z-scores. We recruited 20 subcortical ischemic vascular disease (SIVD) patients who fulfilled the criteria for svMCI...
2017: Frontiers in Aging Neuroscience
Anneke Alkemade, Gilles de Hollander, Max C Keuken, Andreas Schäfer, Derek V M Ott, Johannes Schwarz, David Weise, Sonja A Kotz, Birte U Forstmann
The subthalamic nucleus (STN) plays a crucial role in the surgical treatment of Parkinson's disease (PD). Studies investigating optimal protocols for STN visualization using state of the art magnetic resonance imaging (MRI) techniques have shown that susceptibility weighted images, which display the magnetic susceptibility distribution, yield better results than T1-weighted, T2-weighted, and T2*-weighted contrasts. However, these findings are based on young healthy individuals, and require validation in elderly individuals and persons suffering from PD...
2017: PloS One
Benedikt A Poser, Kawin Setsompop
The SNR and CNR benefits of ultra-high field (UHF) have helped push the envelope of achievable spatial resolution in MRI. For applications based on susceptibility contrast where there is a large CNR gain, high quality sub-millimeter resolution imaging is now being routinely performed, particularly in fMRI and phase imaging/QSM. This has enabled the study of structure and function of very fine-scale structures in the brain. UHF has also helped push the spatial resolution of many other MRI applications as will be outlined in this review...
April 6, 2017: NeuroImage
Elham Esmaeilishirazifard, Daniela De Vizio, Sterghios A Moschos, Tajalli Keshavarz
Quorum sensing molecules (QSMs) are involved in the regulation of complicated processes helping bacterial populations respond to changes in their cell-density. Although the QS gene cluster (comQXPA) has been identified in the genome sequence of some bacilli, the QS system B. licheniformis has not been investigated in detail, and its QSM (ComX pheromone) has not been identified. Given the importance of this antagonistic bacterium as an industrial workhorse, this study was aimed to elucidate B. licheniformis NCIMB-8874 QS...
December 2017: AMB Express
Meng Wang, Hao Wu, Ming Tang, Zhiyong Zhao, Yunli Dang, Can Zhao, Ruolin Liao, Wen Chen, Songnian Fu, Chen Yang, Weijun Tong, Perry Ping Shum, Deming Liu
We proposed and experimentally demonstrated a few mode fiber (FMF) based Raman distributed temperature sensor (RDTS) to extend the sensing distance with enhanced signal-to-noise ratio (SNR) of backscattered anti-Stokes spontaneous Raman scattering. Operating in the quasi-single mode (QSM) with efficient fundamental mode excitement, the FMF allows much larger input pump power before the onset of stimulated Raman scattering compared with the standard single mode fiber (SSMF) and mitigates the detrimental differential mode group delay (DMGD) existing in the conventional multimode fiber (MMF) based RDTS system...
March 6, 2017: Optics Express
Ryota Sato, Toru Shirai, Yo Taniguchi, Takenori Murase, Yoshitaka Bito, Hisaaki Ochi
Quantitative susceptibility mapping (QSM) is a new magnetic resonance imaging (MRI) technique for noninvasively estimating the magnetic susceptibility of biological tissue. Several methods for QSM have been proposed. One of these methods can estimate susceptibility with high accuracy in tissues whose contrast is consistent between magnitude images and susceptibility maps, such as deep gray-matter nuclei. However, the susceptibility of small veins is underestimated and not well depicted by using the above approach, because the contrast of small veins is inconsistent between a magnitude image and a susceptibility map...
March 27, 2017: Magnetic Resonance in Medical Sciences: MRMS
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
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
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
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
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
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
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
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
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
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...
April 1, 2017: NeuroImage
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
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
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