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Magma

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https://www.readbyqxmd.com/read/28695398/variable-slice-thickness-vast-epi-for-the-reduction-of-susceptibility-artifacts-in-whole-brain-ge-epi-at-7-tesla
#1
Sascha Brunheim, Sören Johst, Viktor Pfaffenrot, Stefan Maderwald, Harald H Quick, Benedikt A Poser
OBJECTIVE: A new technique for 2D gradient-recalled echo echo-planar imaging (GE-EPI) termed 'variable slice thickness' (VAST) is proposed, which reduces signal losses caused by through-slice susceptibility artifacts, while keeping the volume repetition time (TR) manageable. The slice thickness is varied across the brain, with thinner slices being used in the inferior brain regions where signal voids are most severe. MATERIALS AND METHODS: Various axial slice thickness schemes with identical whole-brain coverage were compared to regular EPI, which may either suffer from unfeasibly long TR if appropriately thin slices are used throughout, or signal loss if no counter-measures are taken...
July 10, 2017: Magma
https://www.readbyqxmd.com/read/28685373/temperature-dependence-of-1-h-nmr-chemical-shifts-and-its-influence-on-estimated-metabolite-concentrations
#2
Felizitas C Wermter, Nico Mitschke, Christian Bock, Wolfgang Dreher
OBJECTIVES: Temperature dependent chemical shifts of important brain metabolites measured by localised (1)H MRS were investigated to test how the use of incorrect prior knowledge on chemical shifts impairs the quantification of metabolite concentrations. MATERIALS AND METHODS: Phantom measurements on solutions containing 11 metabolites were performed on a 7 T scanner between 1 and 43 °C. The temperature dependence of the chemical shift differences was fitted by a linear model...
July 6, 2017: Magma
https://www.readbyqxmd.com/read/28653214/three-dimensional-black-blood-multi-contrast-carotid-imaging-using-compressed-sensing-a-repeatability-study
#3
Jianmin Yuan, Ammara Usman, Scott A Reid, Kevin F King, Andrew J Patterson, Jonathan H Gillard, Martin J Graves
OBJECTIVE: The purpose of this work is to evaluate the repeatability of a compressed sensing (CS) accelerated multi-contrast carotid protocol at 3 T. MATERIALS AND METHODS: Twelve volunteers and eight patients with carotid disease were scanned on a 3 T MRI scanner using a CS accelerated 3-D black-blood multi-contrast protocol which comprises T 1w, T 2w and PDw without CS, and with a CS factor of 1.5 and 2.0. The volunteers were scanned twice, the lumen/wall area and wall thickness were measured for each scan...
June 26, 2017: Magma
https://www.readbyqxmd.com/read/28631204/adaptive-step-size-lms-improves-ecg-detection-during-mri-at-1-5-and-3%C3%A2-t
#4
André Guillou, Jean-Marc Sellal, Sarah Ménétré, Grégory Petitmangin, Jacques Felblinger, Laurent Bonnemains
OBJECTIVE: We describe a new real-time filter to reduce artefacts on electrocardiogram (ECG) due to magnetic field gradients during MRI. The proposed filter is a least mean square (LMS) filter able to continuously adapt its step size according to the gradient signal of the ongoing MRI acquisition. MATERIALS AND METHODS: We implemented this filter and compared it, within two databases (at 1.5 and 3 T) with over 6000 QRS complexes, to five real-time filtering strategies (no filter, low pass filter, standard LMS, and two other filters optimized within the databases: optimized LMS, and optimized Kalman filter)...
June 19, 2017: Magma
https://www.readbyqxmd.com/read/28631203/assessment-of-mri-contrast-agent-concentration-by-quantitative-susceptibility-mapping-qsm-application-to-estimation-of-cerebral-blood-volume-during-steady-state
#5
Emelie Lind, Linda Knutsson, Robin Kämpe, Freddy Ståhlberg, Ronnie Wirestam
OBJECTIVE: One major issue in dynamic susceptibility contrast MRI (DSC-MRI) is to accurately determine contrast agent (CA) concentration, since T2* relaxivity in vivo is generally unknown and varies between blood and tissue. In this study, quantitative susceptibility mapping (QSM) was used for quantification of CA concentration. MATERIALS AND METHODS: A DSC-MRI protocol, including phase data acquisition, was applied to 20 healthy volunteers in a test-retest study...
June 19, 2017: Magma
https://www.readbyqxmd.com/read/28620752/fatty-metaplasia-quantification-and-impact-on-regional-myocardial-function-as-assessed-by-advanced-cardiac-mr-imaging
#6
Tomas Lapinskas, Bernhard Schnackenburg, Marc Kouwenhoven, Rolf Gebker, Alexander Berger, Remigijus Zaliunas, Burkert Pieske, Sebastian Kelle
OBJECTIVE: This study aimed to investigate the advantages of recently developed cardiac imaging techniques of fat-water separation and feature tracking to characterize better individuals with chronic myocardial infarction (MI). MATERIALS AND METHODS: Twenty patients who had a previous MI underwent CMR imaging. The study protocol included routine cine and late gadolinium enhancement (LGE) technique. In addition, mDixon LGE imaging was performed in every patient. Left ventricular (LV) circumferential (EccLV) and radial (ErrLV) strain were calculated using dedicated software (CMR(42), Circle, Calgary, Canada)...
June 15, 2017: Magma
https://www.readbyqxmd.com/read/28608328/towards-accurate-and-precise-t-1-and-extracellular-volume-mapping-in-the-myocardium-a-guide-to-current-pitfalls-and-their-solutions
#7
REVIEW
Donnie Cameron, Vassilios S Vassiliou, David M Higgins, Peter D Gatehouse
Mapping of the longitudinal relaxation time (T 1) and extracellular volume (ECV) offers a means of identifying pathological changes in myocardial tissue, including diffuse changes that may be invisible to existing T 1-weighted methods. This technique has recently shown strong clinical utility for pathologies such as Anderson-Fabry disease and amyloidosis and has generated clinical interest as a possible means of detecting small changes in diffuse fibrosis; however, scatter in T 1 and ECV estimates offers challenges for detecting these changes, and bias limits comparisons between sites and vendors...
June 12, 2017: Magma
https://www.readbyqxmd.com/read/28608327/diffusional-kurtosis-imaging-dki-incorporation-into-an-intravoxel-incoherent-motion-ivim-mr-model-to-measure-cerebral-hypoperfusion-induced-by-hyperventilation-challenge-in-healthy-subjects
#8
Aude Pavilla, Giulio Gambarota, Alessandro Arrigo, Mehdi Mejdoubi, Régis Duvauferrier, Hervé Saint-Jalmes
OBJECTIVES: The objectives were to investigate the diffusional kurtosis imaging (DKI) incorporation into the intravoxel incoherent motion (IVIM) model for measurements of cerebral hypoperfusion in healthy subjects. MATERIALS AND METHODS: Eight healthy subjects underwent a hyperventilation challenge with a 4-min diffusion weighted imaging protocol, using 8 b values chosen with the Cramer-Rao Lower Bound optimization approach. Four regions of interest in gray matter (GM) were analyzed with the DKI-IVIM model and the bi-exponential IVIM model, for normoventilation and hyperventilation conditions...
June 12, 2017: Magma
https://www.readbyqxmd.com/read/28608326/identification-of-myocardial-diffuse-fibrosis-by-11-heartbeat-molli-t-1-mapping-averaging-to-improve-precision-and-correlation-with-collagen-volume-fraction
#9
Vassilios S Vassiliou, Katharina Wassilew, Donnie Cameron, Ee Ling Heng, Evangelia Nyktari, George Asimakopoulos, Anthony de Souza, Shivraman Giri, Iain Pierce, Andrew Jabbour, David Firmin, Michael Frenneaux, Peter Gatehouse, Dudley J Pennell, Sanjay K Prasad
OBJECTIVES: Our objectives involved identifying whether repeated averaging in basal and mid left ventricular myocardial levels improves precision and correlation with collagen volume fraction for 11 heartbeat MOLLI T 1 mapping versus assessment at a single ventricular level. MATERIALS AND METHODS: For assessment of T 1 mapping precision, a cohort of 15 healthy volunteers underwent two CMR scans on separate days using an 11 heartbeat MOLLI with a 5(3)3 beat scheme to measure native T 1 and a 4(1)3(1)2 beat post-contrast scheme to measure post-contrast T 1, allowing calculation of partition coefficient and ECV...
June 12, 2017: Magma
https://www.readbyqxmd.com/read/28573461/automatic-frequency-and-phase-alignment-of-in-vivo-j-difference-edited-mr-spectra-by-frequency-domain-correlation
#10
Evita C Wiegers, Bart W J Philips, Arend Heerschap, Marinette van der Graaf
OBJECTIVE: J-difference editing is often used to select resonances of compounds with coupled spins in (1)H-MR spectra. Accurate phase and frequency alignment prior to subtracting J-difference-edited MR spectra is important to avoid artefactual contributions to the edited resonance. MATERIALS AND METHODS: In-vivo J-difference-edited MR spectra were aligned by maximizing the normalized scalar product between two spectra (i.e., the correlation over a spectral region)...
June 1, 2017: Magma
https://www.readbyqxmd.com/read/28569376/sex-body-mass-index-and-blood-pressure-are-related-to-aortic-characteristics-in-healthy-young-adults-using-magnetic-resonance-vessel-wall-imaging-the-ambityon-study
#11
Anouk L M Eikendal, Hester M den Ruijter, Cees Haaring, Tobias Saam, Rob J van der Geest, Jos J M Westenberg, Michiel L Bots, Imo E Hoefer, Tim Leiner
OBJECTIVES: More detailed evaluation of atherosclerosis and its key determinants in young individuals is warranted to improve knowledge on the pathophysiology of its development and progression. This study evaluated associations of magnetic resonance imaging (MRI)-derived aortic wall area, wall thickness, and pulse wave velocity (PWV) with cardiovascular risk factors in asymptomatic, young adults. MATERIALS AND METHODS: In 124 adults (age: 25-35 years) from the general population-based Atherosclerosis Monitoring and Biomarker Measurements in the Young study, demography, anthropometry, and blood samples were collected...
May 31, 2017: Magma
https://www.readbyqxmd.com/read/28569375/motion-compensated-data-decomposition-algorithm-to-accelerate-dynamic-cardiac-mri
#12
Azar Tolouee, Javad Alirezaie, Paul Babyn
OBJECTIVES: In dynamic cardiac magnetic resonance imaging (MRI), the spatiotemporal resolution is often limited by low imaging speed. Compressed sensing (CS) theory can be applied to improve imaging speed and spatiotemporal resolution. The combination of compressed sensing and low-rank matrix completion represents an attractive means to further increase imaging speed. By extending prior work, a Motion-Compensated Data Decomposition (MCDD) algorithm is proposed to improve the performance of CS for accelerated dynamic cardiac MRI...
May 31, 2017: Magma
https://www.readbyqxmd.com/read/28569374/quantitative-pulsed-cest-mri-at-a-clinical-3t-mri-system
#13
Julia Stabinska, Tom Cronenberg, Hans-Jörg Wittsack, Rotem Shlomo Lanzman, Anja Müller-Lutz
OBJECTIVES: The goal of this study was to quantify CEST related parameters such as chemical exchange rate and fractional concentration of exchanging protons at a clinical 3T scanner. For this purpose, two CEST quantification approaches-the AREX metric (for 'apparent exchange dependent relaxation'), and the AREX-based Ω-plot method were used. In addition, two different pulsed RF irradiation schemes, using Gaussian-shaped and spin-lock pulses, were compared. MATERIALS AND METHODS: Numerical simulations as well as MRI measurements in phantoms were performed...
May 31, 2017: Magma
https://www.readbyqxmd.com/read/28550650/single-breath-hold-3-d-cine-imaging-of-the-left-ventricle-using-cartesian-sampling
#14
Jens Wetzl, Michaela Schmidt, François Pontana, Benjamin Longère, Felix Lugauer, Andreas Maier, Joachim Hornegger, Christoph Forman
OBJECTIVES: Our objectives were to evaluate a single-breath-hold approach for Cartesian 3-D CINE imaging of the left ventricle with a nearly isotropic resolution of [Formula: see text] and a breath-hold duration of [Formula: see text]19 s against a standard stack of 2-D CINE slices acquired in multiple breath-holds. Validation is performed with data sets from ten healthy volunteers. MATERIALS AND METHODS: A Cartesian sampling pattern based on the spiral phyllotaxis and a compressed sensing reconstruction method are proposed to allow 3-D CINE imaging with high acceleration factors...
May 26, 2017: Magma
https://www.readbyqxmd.com/read/28550649/improved-formula-see-text-determination-in-23-na-35-cl-and-17-o-mri-using-iterative-partial-volume-correction-based-on-1-h-mri-segmentation
#15
Sebastian C Niesporek, Reiner Umathum, Thomas M Fiedler, Peter Bachert, Mark E Ladd, Armin M Nagel
OBJECTIVE: Functional parameters can be measured with the help of quantitative non-proton MRI where exact relaxometry parameters are needed. Investigation of [Formula: see text] is often biased by strong partial volume (PV) effects. Hence, in this work a PV correction algorithm approach was evaluated that uses iteratively adapted [Formula: see text]-values and high-resolution structural (1)H data to determine transverse relaxation in non-proton MRI more accurately. MATERIALS AND METHODS: Simulations, a phantom study and in vivo (23)Na, (17)O and (35)Cl MRI measurements of five healthy volunteers were performed to evaluate the algorithm...
May 26, 2017: Magma
https://www.readbyqxmd.com/read/28455630/relationship-between-carotid-plaque-surface-morphology-and-perfusion-a-3d-dce-mri-study
#16
Jianmin Yuan, Gregory Makris, Andrew Patterson, Ammara Usman, Tilak Das, Andrew Priest, Zhongzhao Teng, Sarah Hilborne, Dario Prudencio, Jonathan Gillard, Martin Graves
OBJECTIVE: This study aims to explore the relationship between plaque surface morphology and neovascularization using a high temporal and spatial resolution 4D contrast-enhanced MRI/MRA sequence. MATERIALS AND METHODS: Twenty one patients with either recent symptoms or a carotid artery stenosis ≥40% were recruited in this study. Plaque surface morphology and luminal stenosis were determined from the arterial phase MRA images. Carotid neovascularization was evaluated by a previously validated pharmacokinetic (PK) modeling approach...
April 28, 2017: Magma
https://www.readbyqxmd.com/read/28455629/validation-of-an-active-shape-model-based-semi-automated-segmentation-algorithm-for-the-analysis-of-thigh-muscle-and-adipose-tissue-cross-sectional-areas
#17
Jana Kemnitz, Felix Eckstein, Adam G Culvenor, Anja Ruhdorfer, Torben Dannhauer, Susanne Ring-Dimitriou, Alexandra M Sänger, Wolfgang Wirth
OBJECTIVE: To validate a semi-automated method for thigh muscle and adipose tissue cross-sectional area (CSA) segmentation from MRI. MATERIALS AND METHODS: An active shape model (ASM) was trained using 113 MRI CSAs from the Osteoarthritis Initiative (OAI) and combined with an active contour model and thresholding-based post-processing steps. This method was applied to 20 other MRIs from the OAI and to baseline and follow-up MRIs from a 12-week lower-limb strengthening or endurance training intervention (n = 35 females)...
April 28, 2017: Magma
https://www.readbyqxmd.com/read/28444504/correction-of-parallel-transmission-using-concurrent-rf-and-gradient-field-monitoring
#18
Mustafa Çavuşoğlu, Benjamin Emanuel Dietrich, David Otto Brunner, Markus Weiger, Klaas Paul Pruessmann
OBJECTIVES: The accuracy and precision of the parallel RF excitations are highly dependent on the spatial and temporal fidelity of the magnetic fields involved in spin excitation. The consistency between the nominal and effective fields is typically limited by the imperfections of the employed hardware existing both in the gradient system and the RF chain. In this work, we experimentally presented highly improved spatially tailored parallel excitations by turning the native hardware accuracy challenge into a measurement and control problem using an advanced field camera technology to fully correct parallel RF transmission experiment...
April 25, 2017: Magma
https://www.readbyqxmd.com/read/28054143/a-low-cost-mr-compatible-ergometer-to-assess-post-exercise-phosphocreatine-recovery-kinetics
#19
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...
June 2017: 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
#20
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...
June 2017: Magma
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