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https://www.readbyqxmd.com/read/28731748/characterizing-time-irreversibility-in-disordered-fermionic-systems-by-the-effect-of-local-perturbations
#1
Shreya Vardhan, Giuseppe De Tomasi, Markus Heyl, Eric J Heller, Frank Pollmann
We study the effects of local perturbations on the dynamics of disordered fermionic systems in order to characterize time irreversibility. We focus on three different systems: the noninteracting Anderson and Aubry-André-Harper (AAH) models and the interacting spinless disordered t-V chain. First, we consider the effect on the full many-body wave functions by measuring the Loschmidt echo (LE). We show that in the extended or ergodic phase the LE decays exponentially fast with time, while in the localized phase the decay is algebraic...
July 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28731616/inversion-recovery-ultrashort-echo-time-imaging-of-ultrashort-t2-tissue-components-in-ovine-brain-at-3%C3%A2-t-a-sequential-d2-o-exchange-study
#2
Shu-Juan Fan, Yajun Ma, Eric Y Chang, Graeme M Bydder, Jiang Du
Inversion recovery ultrashort echo time (IR-UTE) imaging holds the potential to directly characterize MR signals from ultrashort T2 tissue components (STCs), such as collagen in cartilage and myelin in brain. The application of IR-UTE for myelin imaging has been challenging because of the high water content in brain and the possibility that the ultrashort T2 * signals are contaminated by water protons, including those associated with myelin sheaths. This study investigated such a possibility in an ovine brain D2 O exchange model and explored the potential of IR-UTE imaging for the quantification of ultrashort T2 * signals in both white and gray matter at 3 T...
July 21, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28731570/susceptibility-weighted-imaging-and-quantitative-susceptibility-mapping-of-the-cerebral-vasculature-using-ferumoxytol
#3
Saifeng Liu, Jean-Christophe Brisset, Jiani Hu, E Mark Haacke, Yulin Ge
PURPOSE: To demonstrate the potential of imaging cerebral arteries and veins with ferumoxytol using susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM). MATERIALS AND METHODS: The relationships between ferumoxytol concentration and the apparent susceptibility at 1.5T, 3T, and 7T were determined using phantom data; the ability of visualizing subvoxel vessels was evaluated using simulations; and the feasibility of using ferumoxytol to enhance the visibility of small vessels was confirmed in three healthy volunteers at 7T(with doses 1 mg/kg to 4 mg/kg)...
July 21, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28730173/surface-coil-intensity-correction-in-magnetic-resonance-imaging-in-spinal-metastases
#4
Hong Ren, Wei Lin, Xianjun Ding
OBJECTIVE: To evaluate the clinical application of phased-array surface coil intensity correction in magnetic resonance imaging (MRI) in spinal metastases. METHODS: 3 phantoms and 50 patients with a corresponding total number of 80 spinal metastases were included in this study. Fast spin echo T1- and T2- weighted MRI with and without surface coil intensity correction was routinely performed for all phantoms and patients. Phantoms were evaluated by means of variance to mean ratio of signal intensity on both T1- and T2- weighted MRI obtained with and without surface coil intensity correction...
2017: Open Medicine (Warsaw, Poland)
https://www.readbyqxmd.com/read/28729409/comparison-of-anatomic-and-clinical-outcomes-in-patients-undergoing-alternative-initial-noninvasive-testing-strategies-for-the-diagnosis-of-stable-coronary-artery-disease
#5
Idan Roifman, Harindra C Wijeysundera, Peter C Austin, Mohammad R Rezai, Graham A Wright, Jack V Tu
BACKGROUND: The optimal initial noninvasive diagnostic testing strategy for stable coronary artery disease (CAD) is unknown. Although American guidelines recommend an exercise stress test as the first-line test, European guidelines suggest that stress imaging (myocardial perfusion imaging or stress echocardiography) or coronary computed tomography angiography may be preferable. Understanding the relationship between the initial strategy and downstream yield of obstructive CAD and major adverse cardiac events may provide insight as to the optimal strategy...
July 19, 2017: Journal of the American Heart Association
https://www.readbyqxmd.com/read/28729160/echo-time-dependence-of-the-bold-response-transients-a-window-into-brain-functional-physiology
#6
Martin Havlicek, Dimo Ivanov, Benedikt A Poser, Kamil Uludag
The blood oxygenation level-dependent (BOLD) fMRI response to neuronal activation results from a complex interplay of induced metabolic and vascular changes. Thus, its transients, such as initial overshoot and post-stimulus undershoot, provide a window into the dynamic relationships of the underlying physiological variables. In this study, we propose multi-echo fMRI as a tool to investigate the physiological underpinnings of the BOLD signal, in particular, and brain functional physiology, in general. In the human visual cortex at 3 T, we observed that the BOLD response is nonlinearly dependent on echo-time (TE) and the amount of nonlinearity varies during the entire time-course...
July 17, 2017: NeuroImage
https://www.readbyqxmd.com/read/28728755/-magnetic-resonance-in-traumatic-brain-injury-a-comparative-study-of-the-different-conventional-magnetic-resonance-imaging-sequences-and-their-diagnostic-value-in-diffuse-axonal-injury
#7
Marta Cicuendez, Ana Castaño-León, Ana Ramos, Amaya Hilario, Pedro A Gómez, Alfonso Lagares
OBJECTIVE: To compare the identification capability of traumatic axonal injury (TAI) by different sequences on conventional magnetic resonance (MR) studies in traumatic brain injury (TBI) patients. MATERIAL AND METHODS: We retropectevely analyzed 264 TBI patients to whom a MR had been performed in the first 60 days after trauma. All clinical variables related to prognosis were registered, as well as the data from the initial computed tomography. The MR imaging protocol consisted of a 3-plane localizer sequence T1-weighted and T2-weighted fast spin-echo, FLAIR and gradient-echo images (GRET2*)...
July 17, 2017: Neurocirugía
https://www.readbyqxmd.com/read/28728585/neuroscience-in-the-third-dimension-shedding-new-light-on-the-brain-with-tissue-clearing
#8
REVIEW
Robin J Vigouroux, Morgane Belle, Alain Chédotal
For centuries analyses of tissues have depended on sectioning methods. Recent developments of tissue clearing techniques have now opened a segway from studying tissues in 2 dimensions to 3 dimensions. This particular advantage echoes heavily in the field of neuroscience, where in the last several years there has been an active shift towards understanding the complex orchestration of neural circuits. In the past five years, many tissue-clearing protocols have spawned. This is due to varying strength of each clearing protocol to specific applications...
July 20, 2017: Molecular Brain
https://www.readbyqxmd.com/read/28727544/abbreviated-biparametric-prostate-mr-imaging-in-men-with-elevated-prostate-specific-antigen
#9
Christiane K Kuhl, Robin Bruhn, Nils Krämer, Sven Nebelung, Axel Heidenreich, Simone Schrading
Purpose To determine the diagnostic accuracy for clinically significant prostate cancer achieved with abbreviated biparametric prostate magnetic resonance (MR) imaging in comparison with full multiparametric contrast material-enhanced prostate MR imaging in men with elevated prostate-specific antigen (PSA) and negative transrectal ultrasonography (US)-guided biopsy findings; to determine the significant cancer detection rate of biparametric versus full multiparametric contrast-enhanced MR imaging and between-reader agreement for interpretation of biparametric MR imaging...
July 20, 2017: Radiology
https://www.readbyqxmd.com/read/28726843/new-antarctic-iceberg-echoes-old-problem
#10
EDITORIAL
(no author information available yet)
No abstract text is available yet for this article.
July 14, 2017: Nature
https://www.readbyqxmd.com/read/28726335/preperitoneal-fat-as-a-noninvsasive-marker-of-increased-risk-of-severe-non-alcoholic-fatty-liver-disease-in-patients-with-type-2-diabetes
#11
Daniella Braz Parente, Jaime Araújo Oliveira Netso, Pedro Emmanuel Alvarenga Americano Brasil, Fernando Fernandes Paiva, José Pedro Rodrigues Ravani, Marilia Brito Gomes, Valeria Lanzoni, Carlos Frederico Ferreira Campos, Lilian Machado-Silva, Renata Mello Perez, Rosana Souza Rodrigues
BACKGROUND AND AIM: Fat distribution may have prognostic value in the evaluation of non-alcoholic fatty liver disease. This study was conducted to evaluate associations of MRI-measured abdominal fat areas with steatosis, steatohepatitis, and fibrosis, assessed histopathologically, in patients with type 2 diabetes. METHODS: This prospective study included 66 patients with type 2 diabetes (12 males, 54 females, age 26-68 years), without chronic liver disease of other causes...
July 20, 2017: Journal of Gastroenterology and Hepatology
https://www.readbyqxmd.com/read/28722247/left-ventricular-function-and-regional-strain-with-subtly-tagged-steady-state-free-precession-feature-tracking
#12
Eric M Schrauben, Brett R Cowan, Andreas Greiser, Alistair A Young
PURPOSE: To provide regional strain and ventricular volume from a single acquisition, using subtly tagged steady-state free precession (SubTag SSFP) feature tracking. MATERIALS AND METHODS: The effects on regional strain of tag strength in gradient recalled echo (GRE) tagging, flip angle in untagged balanced SSFP, and both in SubTag SSFP were examined in the mid left ventricle of 15 healthy volunteers at 3T. Optimal parameters were determined from varying both tag strength and SSFP flip angle using full tag saturation GRE as the reference standard...
July 19, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28722201/susceptibility-induced-distortion-correction-in-hyperpolarized-echo-planar-imaging
#13
Jack J Miller, Angus Z Lau, Damian J Tyler
PURPOSE: Echo planar imaging is an attractive rapid imaging readout that can image hyperpolarized compounds in vivo. By alternating the sign of the phase encoding gradient waveform, spatial offsets arising from uncertain frequency shifts can be determined. We show here that blip-reversed echo planar imaging can also be used to correct for susceptibility and B0 inhomogeneity effects that would otherwise produce image-domain distortion in the heart. METHODS: Previously acquired blip-reversed cardiac 3D-Spectral-Spatial echo planar imaging volumetric timecourses of hyperpolarized [1-(13) C]pyruvate were distortion corrected by a deformation field estimated by reconstructing signal-to-noise ratio (SNR)-weighted progressively subsampled temporally summed images of each metabolite...
July 19, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28720778/visualization-of-kidney-fibrosis-in-diabetic-nephropathy-by-long-diffusion-tensor-imaging-mri-with-spin-echo-sequence
#14
Jun-Ya Kaimori, Yoshitaka Isaka, Masaki Hatanaka, Satoko Yamamoto, Naotsugu Ichimaru, Akihiko Fujikawa, Hiroshi Shibata, Akira Fujimori, Sosuke Miyoshi, Takashi Yokawa, Kagayaki Kuroda, Toshiki Moriyama, Hiromi Rakugi, Shiro Takahara
Renal fibrosis (RF) is an indicator for progression of chronic kidney disease (CKD). Although diabetic nephropathy (DN) is the leading cause of CKD and end-stage renal disease in Western populations, the ability of MRI to evaluate RF in DN patients has not been determined. As a first step to identify possible MRI methods for RF evaluation, we examined the use of diffusion tensor imaging (DTI) MRI to evaluate RF in a rat model of DN (SHR/NDmcr-cp(cp/cp): SHR/ND). The signal-to-noise ratio in DTI MRI was enhanced using a spin-echo sequence, and a special kidney attachment was developed for long-term stabilization...
July 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28717997/an-enhanced-sensitivity-methyl-1-h-triple-quantum-pulse-scheme-for-measuring-diffusion-constants-of-macromolecules
#15
Rui Huang, Jacob P Brady, Ashok Sekhar, Tairan Yuwen, Lewis E Kay
We present a pulse scheme that exploits methyl (1)H triple-quantum (TQ) coherences for the measurement of diffusion rates of slowly diffusing molecules in solution. It is based on the well-known stimulated echo experiment, with encoding and decoding of TQ coherences. The size of quantifiable diffusion coefficients is thus lowered by an order of magnitude with respect to single-quantum (SQ) approaches. Notably, the sensitivity of the scheme is high, approximately ¾ that of the corresponding single quantum experiment, neglecting relaxation losses, and on the order of a factor of 4 more sensitive than a previously published sequence for AX3 spin systems (Zheng et al...
July 17, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28717625/assessment-of-different-fitting-methods-for-in-vivo-bi-component-t2-analysis-of-human-patellar-tendon-in-magnetic-resonance-imaging
#16
Fang Liu, Richard Kijowski
PURPOSE: To investigate the robustness of four fitting methods for bi-component effective spin-spin T2 (T2(*)) relaxation time analysis of human patellar tendon. METHODS: A three-dimensional (3D) cone ultra-short echo-time (UTE) sequence was performed on the knees of ten healthy volunteers at 3.0T. Four fitting methods incorporating either Gaussian or Rician noise distribution were used for voxel-by-voxel bi-component T2(*) analysis of the patellar tendon. The T2(*) for the short relaxing (T(*)*,s ) and long relaxing (T(*)2,l ) water components and the fraction of the short relaxing water component (fs ) were measured, and different fitting methods were compared using Friedman's and Wilcoxon signed rank tests...
January 2017: Muscles, Ligaments and Tendons Journal
https://www.readbyqxmd.com/read/28716681/mri-magic-angle-effect-in-femorotibial-cartilages-of-the-red-kangaroo
#17
Tonima S Ali, Namal Thibbotuwawa, YuanTong Gu, Konstantin I Momot
OBJECTIVE: Kangaroo knee cartilages are robust tissues that can support knee flexion and endure high levels of compressive stress. This study aimed to develop a detailed understanding of the collagen architecture in kangaroo knee cartilages and thus obtain insights into the biophysical basis of their function. DESIGN: Cylindrical/square plugs from femoral and tibial hyaline cartilage and tibial fibrocartilage were excised from the knees of three adult red kangaroos...
July 14, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28716680/three-dimensional-adiabatic-inversion-recovery-prepared-ultrashort-echo-time-cones-3d-ir-ute-cones-imaging-of-cortical-bone-in-the-hip
#18
Amin Nazaran, Michael Carl, Yajun Ma, Saeed Jerban, Yanchun Zhu, Xing Lu, Jiang Du, Eric Y Chang
PURPOSE: We present three-dimensional adiabatic inversion recovery prepared ultrashort echo time Cones (3D IR-UTE-Cones) imaging of cortical bone in the hip of healthy volunteers using a clinical 3T scanner. METHODS: A 3D IR-UTE-Cones sequence, based on a short pulse excitation followed by a 3D Cones trajectory, with a nominal TE of 32μs, was employed for high contrast morphological imaging of cortical bone in the hip of heathy volunteers. Signals from soft tissues such as muscle and marrow fat were suppressed via adiabatic inversion and signal nulling...
July 14, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28716586/comparison-of-three-dimensional-t1-weighted-magnetic-resonance-and-contrast-enhanced-ultrasound-plaque-images-for-severe-stenosis-of-the-cervical-carotid-artery
#19
Yasuyoshi Shimada, Kohki Oikawa, Shunrou Fujiwara, Yasushi Ogasawara, Yuiko Sato, Shinsuke Narumi, Tadayoshi Kato, Kazumasa Oura, Yasuo Terayama, Makoto Sasaki, Kentaro Fujimoto, Jun Yoshida, Kuniaki Ogasawara
BACKGROUND AND PURPOSE: Magnetic resonance (MR) and contrast-enhanced ultrasound assess characteristics and neovascularization, respectively, of the carotid plaque. The purpose of the present study was to clarify how findings of contrast-enhanced ultrasound plaque imaging are related to those of 3-dimensional (3D) fast spin echo (FSE) T1-weighted MR plaque imaging (WI) in severe stenosis (≥70%) of the cervical carotid artery. METHODS: Fifty-three patients underwent 3D FSE T1-WI and contrast-enhanced ultrasound...
July 14, 2017: Journal of Stroke and Cerebrovascular Diseases: the Official Journal of National Stroke Association
https://www.readbyqxmd.com/read/28716430/non-invasive-evaluation-of-right-ventricular-function-with-real-time-3-d-echocardiography
#20
Ran Chen, Meihua Zhu, Kacie Amacher, Xia Wu, David J Sahn, Muhammad Ashraf
The aim of this study was to evaluate the accuracy and feasibility of real-time 3-D echocardiography (3-DE) in assessing right ventricular (RV) systolic function. A latex balloon was inserted into the right ventricle of 20 freshly harvested pig hearts which were then passively driven by a pulsatile pump apparatus. The RV global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS) and RV ejection fraction (RVEF), derived from 3-DE, as well as the RVEF obtained from 2-D echocardiography (2-DE) were quantified at different stroke volumes (30-70 mL) and compared with sonomicrometry data...
July 14, 2017: Ultrasound in Medicine & Biology
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