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Magma

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https://www.readbyqxmd.com/read/28181027/track-weighted-imaging-methods-extracting-information-from-a-streamlines-tractogram
#1
REVIEW
Fernando Calamante
A whole-brain streamlines data-set (so-called tractogram) generated from diffusion MRI provides a wealth of information regarding structural connectivity in the brain. Besides visualisation strategies, a number of post-processing approaches have been proposed to extract more detailed information from the tractogram. One such approach is based on exploiting the information contained in the tractogram to generate track-weighted (TW) images. In the track-weighted imaging (TWI) approach, a very large number of streamlines are often generated throughout the brain, and an image is then computed based on properties of the streamlines themselves (e...
February 8, 2017: Magma
https://www.readbyqxmd.com/read/28120280/highly-accelerated-self-gated-free-breathing-3d-cardiac-cine-mri-validation-in-assessment-of-left-ventricular-function
#2
Jing Liu, Li Feng, Hsin-Wei Shen, Chengcheng Zhu, Yan Wang, Kanae Mukai, Gabriel C Brooks, Karen Ordovas, David Saloner
OBJECTIVE: This work presents a highly-accelerated, self-gated, free-breathing 3D cardiac cine MRI method for cardiac function assessment. MATERIALS AND METHODS: A golden-ratio profile based variable-density, pseudo-random, Cartesian undersampling scheme was implemented for continuous 3D data acquisition. Respiratory self-gating was achieved by deriving motion signal from the acquired MRI data. A multi-coil compressed sensing technique was employed to reconstruct 4D images (3D+time)...
January 24, 2017: Magma
https://www.readbyqxmd.com/read/28091836/assessment-of-edema-using-stir-via-3d-cardiovascular-magnetic-resonance-imaging-in-patients-with-suspected-myocarditis
#3
Michael Jeserich, Bela Merkely, Pascal Schlosser, Simone Kimmel, Gabor Pavlik, Stephan Achenbach
OBJECTIVE: To evaluate three-dimensional T2-weighted fast spin echo triple inversion recovery sequences (STIR+) for the diagnosis of myocardial edema in patients with suspected early myocarditis after respiratory or gastrointestinal tract viral infection and at follow-up. MATERIALS AND METHODS: We prospectively examined 28 patients with suspected myocarditis and 37 controls matched for gender and age. An ECG-triggered STIR+ was used to cover the entire left ventricle in short-axis images with 10-mm slice thickness and no interslice gap...
January 16, 2017: Magma
https://www.readbyqxmd.com/read/28070869/fast-t1-and-t2-mapping-methods-the-zoomed-u-flare-sequence-compared-with-epi-and-snapshot-flash-for-abdominal-imaging-at-11-7-tesla
#4
Géraldine Pastor, María Jiménez-González, Sandra Plaza-García, Marta Beraza, Torsten Reese
OBJECTIVE: A newly adapted zoomed ultrafast low-angle RARE (U-FLARE) sequence is described for abdominal imaging applications at 11.7 Tesla and compared with the standard echo-plannar imaging (EPI) and snapshot fast low angle shot (FLASH) methods. MATERIALS AND METHODS: Ultrafast EPI and snapshot-FLASH protocols were evaluated to determine relaxation times in phantoms and in the mouse kidney in vivo. Owing to their apparent shortcomings, imaging artefacts, signal-to-noise ratio (SNR), and variability in the determination of relaxation times, these methods are compared with the newly implemented zoomed U-FLARE sequence...
January 9, 2017: Magma
https://www.readbyqxmd.com/read/28063096/feasibility-of-in-vivo-three-dimensional-t-2-mapping-using-dicarboxy-proxyl-and-cw-epr-based-single-point-imaging
#5
Harue Kubota, Denis A Komarov, Hironobu Yasui, Shingo Matsumoto, Osamu Inanami, Igor A Kirilyuk, Valery V Khramtsov, Hiroshi Hirata
OBJECTIVES: The aim of this study was to demonstrate the feasibility of in vivo three-dimensional (3D) relaxation time T 2(*) mapping of a dicarboxy-PROXYL radical using continuous-wave electron paramagnetic resonance (CW-EPR) imaging. MATERIALS AND METHODS: Isotopically substituted dicarboxy-PROXYL radicals, 3,4-dicarboxy-2,2,5,5-tetra((2)H3)methylpyrrolidin-(3,4-(2)H2)-(1-(15)N)-1-oxyl ((2)H,(15)N-DCP) and 3,4-dicarboxy-2,2,5,5-tetra((2)H3)methylpyrrolidin-(3,4-(2)H2)-1-oxyl ((2)H-DCP), were used in the study...
January 6, 2017: Magma
https://www.readbyqxmd.com/read/28054143/a-low-cost-mr-compatible-ergometer-to-assess-post-exercise-phosphocreatine-recovery-kinetics
#6
Niels D Naimon, Jerzy Walczyk, James S Babb, Oleksandr Khegai, Xuejiao Che, Leeor Alon, Ravinder R Regatte, Ryan Brown, Prodromos Parasoglou
OBJECTIVE: To develop a low-cost pedal ergometer compatible with ultrahigh (7 T) field MR systems to reliably quantify metabolic parameters in human lower leg muscle using phosphorus magnetic resonance spectroscopy. MATERIALS AND METHODS: We constructed an MR compatible ergometer using commercially available materials and elastic bands that provide resistance to movement. We recruited ten healthy subjects (eight men and two women, mean age ± standard deviation: 32...
January 4, 2017: Magma
https://www.readbyqxmd.com/read/28000087/the-effect-of-diffusion-gradient-direction-number-on-corticospinal-tractography-in-the-human-brain-an-along-tract-analysis
#7
Claudia Testa, Stefania Evangelisti, Mariagrazia Popeo, Stefano Zanigni, Laura Ludovica Gramegna, Paola Fantazzini, Caterina Tonon, David Neil Manners, Raffaele Lodi
OBJECTIVES: We evaluated diffusion imaging measures of the corticospinal tract obtained with a probabilistic tractography algorithm applied to data of two acquisition protocols based on different numbers of diffusion gradient directions (NDGDs). MATERIALS AND METHODS: The corticospinal tracts (CST) of 18 healthy subjects were delineated using 22 and 66-NDGD data. An along-tract analysis of diffusion metrics was performed to detect possible local differences due to NDGD...
December 20, 2016: Magma
https://www.readbyqxmd.com/read/27981396/semi-automated-myocardial-segmentation-of-bright%C3%A2-blood-multi-gradient-echo-images-improves-reproducibility-of-myocardial-contours-and-t2-determination
#8
Pandji Triadyaksa, Niek H J Prakken, Jelle Overbosch, Robin B Peters, J Martijn van Swieten, Matthijs Oudkerk, Paul E Sijens
OBJECTIVES: Early detection of iron loading is affected by the reproducibility of myocardial contour assessment. A novel semi-automatic myocardial segmentation method is presented on contrast-optimized composite images and compared to the results of manual drawing. MATERIALS AND METHODS: Fifty-one short-axis slices at basal, mid-ventricular and apical locations from 17 patients were acquired by bright blood multi-gradient echo MRI. Four observers produced semi-automatic and manual myocardial contours on contrast-optimized composite images...
December 16, 2016: Magma
https://www.readbyqxmd.com/read/27981395/evaluation-of-exposure-to-ultra-high-static-magnetic-fields-during-activities-around-human-mri-scanners
#9
Mahsa Fatahi, Jolanta Karpowicz, Krzysztof Gryz, Amirmohammad Fattahi, Georg Rose, Oliver Speck
OBJECTIVE: To assess the individual exposure to the static magnetic field (SMF) and the motion-induced time-varying magnetic field (TVMF) generated by activities in an inhomogeneous SMF near high and ultra-high field magnetic resonance imaging (MRI) scanners. The study provides information on the level of exposure to high and ultra-high field MRI scanners during research activities. MATERIALS AND METHODS: A three-axis Hall magnetometer was used to determine the SMF and TVMF around human 3- and 7-Tesla (T) MRI systems...
December 16, 2016: Magma
https://www.readbyqxmd.com/read/27943055/reproducible-segmentation-of-white-matter-hyperintensities-using-a-new-statistical-definition
#10
Soheil Damangir, Eric Westman, Andrew Simmons, Hugo Vrenken, Lars-Olof Wahlund, Gabriela Spulber
OBJECTIVES: We present a method based on a proposed statistical definition of white matter hyperintensities (WMH), which can work with any combination of conventional magnetic resonance (MR) sequences without depending on manually delineated samples. MATERIALS AND METHODS: T1-weighted, T2-weighted, FLAIR, and PD sequences acquired at 1.5 Tesla from 119 subjects from the Kings Health Partners-Dementia Case Register (healthy controls, mild cognitive impairment, Alzheimer's disease) were used...
December 9, 2016: Magma
https://www.readbyqxmd.com/read/27394911/assessment-of-the-myelin-water-fraction-in-rodent-spinal-cord-using-t2-prepared-ultrashort-echo-time-mri
#11
Tim Klasen, Cornelius Faber
OBJECTIVE: Multi-component T2 relaxation allows for assessing the myelin water fraction in nervous tissue, providing a surrogate marker for demyelination. The assessment of the number and distribution of different T2 components for devising exact models of tissue relaxation has been limited by T2 sampling with conventional MR methods. MATERIALS AND METHODS: A T2-prepared UTE sequence was used to assess multicomponent T2 relaxation at 9.4 T of fixed mouse and rat spinal cord samples and of mouse spinal cord in vivo...
December 2016: Magma
https://www.readbyqxmd.com/read/27393351/reproducibility-of-macromolecule-suppressed-gaba-measurement-using-motion-and-shim-navigated-mega-special-with-lcmodel-jmrui-and-gannet
#12
Muhammad G Saleh, Jamie Near, Alqadafi Alhamud, Frances Robertson, André J W van der Kouwe, Ernesta M Meintjes
OBJECTIVE: Measuring the pure form of GABA has become increasingly important because of its association with behaviour and certain pathologies. The aim of this study was to assess the reproducibility of GABA measurements using a shim and motion navigated MEGA-SPECIAL sequence with LCModel, jMRUI and GANNET software. MATERIALS AND METHODS: Motion and shim navigated MEGA-SPECIAL scans were acquired in 20 healthy subjects. Two acquisitions were performed for each of two regions: the anterior cingulate (ACC) and medial-parietal (PAR) cortices...
December 2016: Magma
https://www.readbyqxmd.com/read/27384463/magnetization-transfer-imaging-of-cortical-bone-in-vivo-using-a-zero-echo-time-sequence-in-mice-at-4-7%C3%A2-t-a-feasibility-study
#13
Magda Marcon, Markus Weiger, Daniel Keller, Moritz C Wurnig, Christian Eberhardt, Daniel Eberli, Andreas Boss
OBJECTIVE: To investigate the feasibility of magnetization transfer (MT) imaging in mice in vivo for the assessment of cortical bone. MATERIALS AND METHODS: MT-zero echo time data were acquired at 4.7 T in six mice using MT preparation pulses with two different flip angles (FAs) and a series of ten different off-resonance frequencies (500-15000 Hz). Regions of interest were drawn at multiple levels of the femoral cortical bone. The MT ratio (MTR) was computed for each combination of FAs and off-resonance frequencies...
December 2016: Magma
https://www.readbyqxmd.com/read/27333937/quantitative-t1-and-t2-mri-signal-characteristics-in-the-human-brain-different-patterns-of-mr-contrasts-in-normal-ageing
#14
Michael J Knight, Bryony McCann, Demitra Tsivos, Elizabeth Couthard, Risto A Kauppinen
OBJECTIVE: The objective of this study was to examine age-dependent changes in both T1-weighted and T2-weighted image contrasts and spin-echo T2 relaxation time in the human brain during healthy ageing. METHODS: A total of 37 participants between the ages of 49 and 87 years old were scanned with a 3 Tesla system, using T1-weighted, T2 weighted and quantitative spin-echo T2 imaging. Contrast between image intensities and T2 values was calculated for various regions, including between individual hippocampal subfields...
December 2016: Magma
https://www.readbyqxmd.com/read/27295051/dynamic-susceptibility-contrast-perfusion-mri-using-phase-based-venous-output-functions-comparison-with-pseudo-continuous-arterial-spin-labelling-and-assessment-of-contrast-agent-concentration-in-large-veins
#15
Ronnie Wirestam, Emelie Lind, André Ahlgren, Freddy Ståhlberg, Linda Knutsson
OBJECTIVES: Contrast agent (CA) relaxivities are generally not well established in vivo, and the relationship between frequency/phase shift and magnetic susceptibility might be a useful alternative for CA quantification. MATERIALS AND METHODS: Twenty volunteers (25-84 years old) were investigated using test-retest pre-bolus dynamic susceptibility-contrast (DSC) magnetic resonance imaging (MRI). The pre-bolus phase-based venous output function (VOF) time integral was used for arterial input function (AIF) rescaling...
December 2016: Magma
https://www.readbyqxmd.com/read/27260664/denoising-of-mr-spectroscopic-imaging-data-using-statistical-selection-of-principal-components
#16
Abas Abdoli, Radka Stoyanova, Andrew A Maudsley
OBJECTIVES: To evaluate a new denoising method for MR spectroscopic imaging (MRSI) data based on selection of signal-related principal components (SSPCs) from principal components analysis (PCA). MATERIALS AND METHODS: A PCA-based method was implemented for selection of signal-related PCs and denoising achieved by reconstructing the original data set utilizing only these PCs. Performance was evaluated using simulated MRSI data and two volumetric in vivo MRSIs of human brain, from a normal subject and a patient with a brain tumor, using variable signal-to-noise ratios (SNRs), metabolite peak areas, Cramer-Rao bounds (CRBs) of fitted metabolite peak areas and metabolite linewidth...
December 2016: Magma
https://www.readbyqxmd.com/read/27225871/three-dimensional-echo-planar-cine-imaging-of-cerebral-blood-supply-using-arterial-spin-labeling
#17
Manoj Shrestha, Toralf Mildner, Torsten Schlumm, Scott Haile Robertson, Harald Möller
OBJECTIVE: Echo-planar imaging (EPI) with CYlindrical Center-out spatiaL Encoding (EPICYCLE) is introduced as a novel hybrid three-dimensional (3D) EPI technique. Its suitability for the tracking of a short bolus created by pseudo-continuous arterial spin labeling (pCASL) through the cerebral vasculature is demonstrated. MATERIALS AND METHODS: EPICYCLE acquires two-dimensional planes of k-space along center-out trajectories. These "spokes" are rotated from shot to shot about a common axis to encode a k-space cylinder...
December 2016: Magma
https://www.readbyqxmd.com/read/27160299/mri-based-assessment-of-liver-perfusion-and-hepatocyte-injury-in-the-murine-model-of-acute-hepatitis
#18
Katarzyna Byk, Krzysztof Jasinski, Zaneta Bartel, Agnieszka Jasztal, Barbara Sitek, Boguslaw Tomanek, Stefan Chlopicki, Tomasz Skorka
OBJECTIVE: To assess alterations in perfusion and liver function in the concanavalin A (ConA)-induced mouse model of acute liver failure (ALF) using two magnetic resonance imaging (MRI)-based methods: dynamic contrast-enhanced MRI (DCE-MRI) with Gd-EOB-DTPA contrast agent and arterial spin labelling (ASL). MATERIALS AND METHODS: BALB/c mice were studied using a 9.4 T MRI system. The IntraGateFLASH(TM) and FAIR-EPI pulse sequences were used for optimum mouse abdomen imaging...
December 2016: Magma
https://www.readbyqxmd.com/read/27844220/respiratory-optimized-data-selection-for-more-resilient-self-navigated-whole-heart-coronary-mr-angiography
#19
Jerome Chaptinel, Davide Piccini, Gabriele Bonanno, Simone Coppo, Pierre Monney, Matthias Stuber, Juerg Schwitter
OBJECTIVES: Our objective was to test a data-exclusion strategy for respiratory motion suppression by retrospectively eliminating data acquired at extreme respiratory positions for improved coronary vessel sharpness (VS) of 1-D self-navigated 3-D radial whole-heart coronary angiography acquisitions. MATERIALS AND METHODS: 3-D radial self-navigated acquisitions were performed on a 1.5T scanner in volunteers during free-breathing (n = 8), in coached volunteers (n = 13) who were asked to breathe in a controlled manner to mimic cardiovascular patients presenting with Cheyne-Stokes breathing, and in free-breathing patients (n = 20)...
November 14, 2016: Magma
https://www.readbyqxmd.com/read/27822656/k-space-data-processing-for-magnetic-resonance-elastography-mre
#20
Nadège Corbin, Elodie Breton, Michel de Mathelin, Jonathan Vappou
OBJECTIVE: Magnetic resonance elastography (MRE) requires substantial data processing based on phase image reconstruction, wave enhancement, and inverse problem solving. The objective of this study is to propose a new, fast MRE method based on MR raw data processing, particularly adapted to applications requiring fast MRE measurement or high elastogram update rate. MATERIALS AND METHODS: The proposed method allows measuring tissue elasticity directly from raw data without prior phase image reconstruction and without phase unwrapping...
November 7, 2016: Magma
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