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Magnetic Resonance Imaging

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https://www.readbyqxmd.com/read/28917813/structural-impacts-on-the-timing-and-amplitude-of-the-negative-bold-response
#1
David Provencher, Alexandre Bizeau, Guillaume Gilbert, Yves Bérubé-Lauzière, Kevin Whittingstall
The positive (PBR) and negative BOLD responses (NBR) arising in task-fMRI display varying magnitudes and dynamics across voxels. While the effects of structure, particularly of veins, on the PBR have been studied, little is known of NBR-structure relationships. Like the PBR, the NBR is often used as a surrogate marker of neuronal activation in both basic and clinical research and assessing its relationship with cortical structure may help interpret group differences. We therefore investigated how local structure affects BOLD amplitude and timing in PBR and NBR areas using multi-band fMRI during visual stimulation to obtain high temporal resolution (TR=0...
September 13, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28917812/a-minimum-phase-shinnar-le-roux-spectral-spatial-excitation-rf-pulse-for-simultaneous-water-and-lipid-suppression-in-1-h-mrsi-of-body-extremities
#2
Paul Kyu Han, Chao Ma, Kexin Deng, Shuang Hu, Kyung-Wook Jee, Kui Ying, Yen-Lin Chen, Georges El Fakhri
PURPOSE: To develop a spectral-spatial (SPSP) excitation RF pulse for simultaneous water and lipid suppression in proton ((1)H) magnetic resonance spectroscopic imaging (MRSI) of body extremities. METHODS: An SPSP excitation pulse is designed to excite Creatine (Cr) and Choline (Cho) metabolite signals while suppressing the overwhelming water and lipid signals. The SPSP pulse is designed using a recently proposed multidimensional Shinnar-Le Roux (SLR) RF pulse design method...
September 13, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28870515/mri-characteristics-of-the-glia-limitans-externa-a-7t-study
#3
Kiyotaka Suzuki, Kenichi Yamada, Kazunori Nakada, Yuji Suzuki, Masaki Watanabe, Ingrid L Kwee, Tsutomu Nakada
PURPOSE: To perform a systematic analysis of the intrinsic contrast parameters of the FLAIR hyperintense rim (FHR), a thin layer of high intensity covering the entire surface of the cerebral cortex detected on fluid-attenuated inversion recovery (FLAIR) sequence T2 weighted imaging performed on a 7T system, in an attempt to identify its anatomical correlate. METHODS: Fast spin echo inversion recovery (FSE-IR) and cardiac-gated fast spin echo (FSE) images were obtained with defined parameters in eight normal volunteers on a 7 T MRI system to determine T2 and proton density, T1 characteristics...
September 9, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28893660/a-new-rf-transmit-coil-for-foot-and-ankle-imaging-at-7t-mri
#4
Tales Santini, Junghwan Kim, Sossena Wood, Narayanan Krishnamurthy, Nadim Farhat, Carlos Maciel, Shailesh Raval, Tiejun Zhao, Tamer Ibrahim
A four-channel Tic-Tac-Toe (TTT) transmit RF coil was designed and constructed for foot and ankle imaging at 7T MRI. Numerical simulations using an in-house developed FDTD package and experimental analyses using a homogenous phantom show an excellent agreement in terms of B1(+) field distribution and s-parameters. Simulations performed on an anatomically detailed human lower leg model demonstrated an B1(+) field distribution with a coefficient of variation (CV) of 23.9%/15.6%/28.8% and average B1(+) of 0.33μT/0...
September 8, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28890384/design-strategies-for-improved-velocity-selective-pulse-sequences
#5
Gerald B Matson
Over the years, a variety of MRI methods have been developed for visualizing or measuring blood flow without the use of contrast agents. One particular class of methods uses flow-encoding gradients associated with an RF pulse sequence to distinguish spins in flowing blood from stationary spins. While a strength of these particular methods is that, in general, they can be tailored to capture a desired range of blood flow, such sequences either do not provide a sharp transition from stationary spins to flowing spins, or else are long, generating relaxation losses and undesirable SAR, and have limited immunity to resonance offsets and to RF inhomogeneity...
September 7, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28888770/test-retest-reliability-of-cerebral-blood-flow-in-healthy-individuals-using-arterial-spin-labeling-findings-from-the-embarc-study
#6
Jorge R C Almeida, Tsafrir Greenberg, Hanzhang Lu, Henry W Chase, Jay Fournier, Crystal M Cooper, Thilo Deckersbach, Phil Adams, Thomas Carmody, Mauricio Fava, Benji Kurian, Patrick J McGrath, Melvin McInnis, Maria A Oquendo, Ramin Parsey, Myrna Weissman, Madhukar Trivedi, Mary L Phillips
INTRODUCTION: Previous investigations of test-retest reliability of cerebral blood flow (CBF) at rest measured with pseudo-continuous Arterial Spin Labeling (pCASL) demonstrated good reliability, but are limited by the use of similar scanner platforms. In the present study we examined test-retest reliability of CBF in regions implicated in emotion and the default mode network. MATERIAL AND METHODS: We measured absolute and relative CBF at rest in thirty-one healthy subjects in two scan sessions, one week apart, at four different sites and three different scan platforms...
September 6, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28888769/inter-vender-and-test-retest-reliabilities-of-resting-state-functional-magnetic-resonance-imaging-implications-for-multi-center-imaging-studies
#7
Hyeong Su An, Won-Jin Moon, Jae-Kyun Ryu, Ju Yeon Park, Won Sung Yun, Jin Woo Choi, Geon-Ho Jahng, Jang-Yeon Park
This prospective multi-center study aimed to evaluate the inter-vendor and test-retest reliabilities of resting-state functional magnetic resonance imaging (RS-fMRI) by assessing the temporal signal-to-noise ratio (tSNR) and functional connectivity. Study included 10 healthy subjects and each subject was scanned using three 3T MR scanners (GE Signa HDxt, Siemens Skyra, and Philips Achieva) in two sessions. The tSNR was calculated from the time course data. Inter-vendor and test-retest reliabilities were assessed with intra-class correlation coefficients (ICCs) derived from variant component analysis...
September 6, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28887207/extent-of-size-shape-and-systolic-variability-of-the-left-ventricular-outflow-tract-in-aortic-stenosis-determined-by-phase-contrast-mri
#8
Florian Sagmeister, Markus Weininger, Sebastian Herrmann, Peter Bernhardt, Volker Rasche, Robert Bauernschmitt, Andreas Liebold, Herbert Köstler, Frank Weidemann, Meinrad Beer
PURPOSE: Left ventricular outflow tract (LVOT) dimensions are important for calculation of aortic valve areas and planning of valve repair. Mostly, LVOT areas are calculated from echocardiographic longitudinal measurements with the assumption of a round shape. Here, orthogonal phase contrast (PC) MRI with dynamic assessment of LVOT was compared to standard longitudinal cine MRI and 2D echocardiography. METHODS: In 19 patients with aortic stenosis (5 female; 69±10years), LVOT areas were determined on orthogonal PC images, either by planimetry (Aplan) or by two-diameter measurement (Aellip)...
September 5, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28887206/reproducibility-and-relative-stability-in-magnetic-resonance-imaging-indices-of-tumor-vascular-physiology-over-a-period-of-24h-in-a-rat-9l-gliosarcoma-model
#9
Tavarekere N Nagaraja, Rasha Elmghirbi, Stephen L Brown, Lonni R Schultz, Ian Y Lee, Kelly A Keenan, Swayamprava Panda, Glauber Cabral, Tom Mikkelsen, James R Ewing
PURPOSE: The objective was to study temporal changes in tumor vascular physiological indices in a period of 24h in a 9L gliosarcoma rat model. METHODS: Fischer-344 rats (N=14) were orthotopically implanted with 9L cells. At 2weeks post-implantation, they were imaged twice in a 24h interval using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Data-driven model-selection-based analysis was used to segment tumor regions with varying vascular permeability characteristics...
September 5, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28870514/microstructure-informed-slow-diffusion-tractography-in-humans-enhances-visualisation-of-fibre-pathways
#10
Farida Grinberg, Ivan I Maximov, Ezequiel Farrher, N Jon Shah
Conventional fibre tractography methods based on diffusion tensor imaging exploit diffusion anisotropy and directionality in the range of low diffusion weightings (b-values). High b-value Biexponential Diffusion Tensor Analysis reported previously has demonstrated that fractional anisotropy of the slow diffusion component is essentially higher than that of conventional diffusion tensor imaging whereas popular compartment models associate this slow diffusion component with axonal water fraction. One of the primary aims of this study is to elucidate the feasibility and potential benefits of "microstructure-informed" whole-brain slow-diffusion fibre tracking (SDIFT) in humans...
September 1, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28867671/the-development-and-optimisation-of-3d-black-blood-r2-mapping-of-the-carotid-artery-wall
#11
Jianmin Yuan, Martin J Graves, Andrew J Patterson, Andrew N Priest, Pascal P R Ruetten, Ammara Usman, Jonathan H Gillard
PURPOSE: To develop and optimise a 3D black-blood R2* mapping sequence for imaging the carotid artery wall, using optimal blood suppression and k-space view ordering. METHODS: Two different blood suppression preparation methods were used; Delay Alternating with Nutation for Tailored Excitation (DANTE) and improved Motion Sensitive Driven Equilibrium (iMSDE) were each combined with a three-dimensional (3D) multi-echo Fast Spoiled GRadient echo (ME-FSPGR) readout...
September 1, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28867670/reduced-distortion-artifact-whole-brain-cbf-mapping-using-blip-reversed-non-segmented-3d-echo-planar-imaging-with-pseudo-continuous-arterial-spin-labeling
#12
Neville D Gai, Yi Yu Chou, Dzung Pham, John A Butman
PURPOSE: To implement and evaluate interleaved blip-up, blip-down, non-segmented 3D echo planar imaging (EPI) with pseudo-continuous arterial spin labeling (pCASL) and post-processing for reduced susceptibility artifact cerebral blood flow (CBF) maps. MATERIALS AND METHODS: 3D EPI non-segmented acquisition with a pCASL labeling sequence was modified to include alternating k-space coverage along phase encoding direction (referred to as "blip-reversed") for alternating dynamic acquisitions of control and label pairs...
September 1, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28867669/constrained-data-extrapolation-code-a-new-approach-for-high-definition-vascular-imaging-from-low-resolution-data
#13
Yang Song, Ehsan Hamtaei, Sean K Sethi, Guang Yang, Haibin Xie, E Mark Haacke
PURPOSE: To introduce a new approach to reconstruct high definition vascular images using COnstrained Data Extrapolation (CODE) and evaluate its capability in estimating vessel area and stenosis. MATERIALS AND METHODS: CODE is based on the constraint that the full width half maximum of a vessel can be accurately estimated and, since it represents the best estimate for the width of the object, higher k-space data can be generated from this information. To demonstrate the potential of extracting high definition vessel edges using low resolution data, both simulated and human data were analyzed to better visualize the vessels and to quantify both area and stenosis measurements...
September 1, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28867668/mri-protocol-optimization-for-quantitative-dce-mri-of-the-spine
#14
Cristina Lavini, Gem Kramer, Indra Pieters-den Bos, Otto Hoekstra, J Tim Marcus
PURPOSE: In this study we systematically investigated different Dynamic Contrast Enhancement (DCE)-MRI protocols in the spine, with the goal of finding an optimal protocol that provides data suitable for quantitative pharmacokinetic modelling (PKM). MATERIALS AND METHODS: In 13 patients referred for MRI of the spine, DCE-MRI of the spine was performed with 2D and 3D MRI protocols on a 3T Philips Ingenuity MR system. A standard bolus of contrast agent (Dotarem - 0...
September 1, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28866387/static-and-dynamic-liver-stiffness-an-ex-vivo-porcine-liver-study-using-mr-elastography
#15
Chun Yang, Meng Yin, Kevin J Glaser, Xiangyang Zhu, Kai Xu, Richard L Ehman, Jun Chen
Magnetic resonance elastography (MRE) is an MRI-based noninvasive technique for quantitatively assessing tissue stiffness. The hypothesis of this study is that stiffness increases with portal pressure. We further hypothesized that the rate of stiffness change with pressure would be larger in liver tissue treated to simulate the stiffening effects of fibrosis. In agreement with our hypothesis, the formalin-treated livers were stiffer than the untreated livers, and in both groups the liver stiffness increased with portal venous pressure...
September 1, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28855113/fpga-implementation-of-real-time-sense-reconstruction-using-pre-scan-and-emaps-sensitivities
#16
Muhammad Faisal Siddiqui, Ahmed Wasif Reza, Abubakr Shafique, Hammad Omer, Jeevan Kanesan
Sensitivity Encoding (SENSE) is a widely used technique in Parallel Magnetic Resonance Imaging (MRI) to reduce scan time. Reconfigurable hardware based architecture for SENSE can potentially provide image reconstruction with much less computation time. Application specific hardware platform for SENSE may dramatically increase the power efficiency of the system and can decrease the execution time to obtain MR images. A new implementation of SENSE on Field Programmable Gate Array (FPGA) is presented in this study, which provides real-time SENSE reconstruction right on the receiver coil data acquisition system with no need to transfer the raw data to the MRI server, thereby minimizing the transmission noise and memory usage...
August 30, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28807750/high-resolution-simultaneous-imaging-of-intracranial-and-extracranial-arterial-wall-with-improved-cerebrospinal-fluid-suppression
#17
Lei Zhang, Na Zhang, Jun Wu, Xin Liu, Yiu-Cho Chung
PURPOSE: To develop a technique for three dimensional (3D) high resolution joint imaging of intracranial and extracranial arterial walls with improved cerebrospinal fluid (CSF) suppression and good blood suppression based on T1 weighted sampling perfection with application optimized contrast using different angle evolutions (T1w-SPACE) and to compare this technique (hereafter, iSPACE) with alternating with nutation for tailored excitation (DANTE) prepared SPACE sequence (DANTE-SPACE) for their CSF suppression performance around the mid cerebral arteries (MCA) and blood suppression at carotid arteries...
August 12, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28827099/4d-cardiac-imaging-at-clinical-3-0t-provides-accurate-assessment-of-murine-myocardial-function-and-viability
#18
Lindsey A Crowe, Fabrizio Montecucco, Federico Carbone, Iris Friedli, Anne-Lise Hachulla, Vincent Braunersreuther, François Mach, Jean-Paul Vallée
OBJECTIVES: We validate a 4D strategy tailored for 3T clinical systems to simultaneously quantify function and infarct size in wild type mice after ischemia/reperfusion, with improved spatial and temporal resolution by comparison to previous published protocols using clinical field MRI systems. METHODS: C57BL/6J mice underwent 60min ischemia/reperfusion (n=14) or were controls without surgery (n=6). Twenty-four hours after surgery mice were imaged with gadolinium injection and sacrificed for post-mortem MRI and histology with serum also taken for Troponin I levels...
August 5, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28827098/diagnostic-accuracy-of-automatic-normalization-of-cbv-in-glioma-grading-using-t1-weighted-dce-mri
#19
Prativa Sahoo, Rakesh K Gupta, Pradeep K Gupta, Ashish Awasthi, Chandra M Pandey, Mudit Gupta, Rana Patir, Sandeep Vaishya, Sunita Ahlawat, Indrajit Saha
PURPOSE: Aim of this retrospective study was to compare diagnostic accuracy of proposed automatic normalization method to quantify the relative cerebral blood volume (rCBV) with existing contra-lateral region of interest (ROI) based CBV normalization method for glioma grading using T1-weighted dynamic contrast enhanced MRI (DCE-MRI). MATERIAL AND METHODS: Sixty patients with histologically confirmed gliomas were included in this study retrospectively. CBV maps were generated using T1-weighted DCE-MRI and are normalized by contralateral ROI based method (rCBV_contra), unaffected white matter (rCBV_WM) and unaffected gray matter (rCBV_GM), the latter two of these were generated automatically...
August 4, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28782677/the-value-of-eswan-in-diagnosis-and-differential-diagnosis-of-prostate-cancer-preliminary-study
#20
Jian-Ying Xin, Shan-Shan Gao, Jin-Gang Liu, Cheng-Feng Sun, Yu Han, Xi-He Sun, Xi-Zhen Wang, Bin Wang
OBJECTIVE: To evaluate the value of enhanced T2 star-weighted angiography (ESWAN) in diagnosis and differential diagnosis of prostate cancer by comparing the multiple indices of ESWAN in benign prostatic hyperplasia (BPH), prostate cancer (PCa) and the normal peripheral zone (PZ). METHODS: Traditional MRI and ESWAN were performed on forty-nine clinically-diagnosed PCa patients, sixty BPH patients, and forty-six normal adult males. The ESWAN indices (magnitude value, phase value, R2* value and T2* value) measured on different regions of interest (ROIs) were analyzed...
August 3, 2017: Magnetic Resonance Imaging
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