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Magma

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https://www.readbyqxmd.com/read/28921052/in-vitro-evaluation-of-flow-patterns-and-turbulent-kinetic-energy-in-trans-catheter-aortic-valve-prostheses
#1
Daniel Giese, Kilian Weiss, Bettina Baeßler, Navid Madershahian, Yeong-Hoon Choi, David Maintz, Alexander C Bunck
OBJECTIVES: The objective of the current work was to evaluate flow and turbulent kinetic energy in different transcatheter aortic valve implants using highly undersampled time-resolved multi-point 3-directional phase-contrast measurements (4D Flow MRI) in an in vitro setup. MATERIALS AND METHODS: A pulsatile flow setup was used with a compliant tubing mimicking a stiff left ventricular outflow tract and ascending aorta. Five different implants were measured using a highly undersampled multi-point 4D Flow MRI sequence...
September 18, 2017: Magma
https://www.readbyqxmd.com/read/28914389/state-of-the-art-review-stress-t1-mapping-technical-considerations-pitfalls-and-emerging-clinical-applications
#2
REVIEW
Stefan K Piechnik, Stefan Neubauer, Vanessa M Ferreira
In vivo mapping of the myocardial T1 relaxation time has recently attained wide clinical validation of its potential utility. In this review, we address the basic principles of the T1 mapping techniques, with particular attention to the emerging application of vasodilatory stress agents to interrogate the myocardial microvascular compartment, and differences between commonly used T1 mapping methods when applied in clinical practice.
September 15, 2017: Magma
https://www.readbyqxmd.com/read/28894997/a-novel-framework-for-evaluating-the-image-accuracy-of-dynamic-mri-and-the-application-on-accelerated-breast-dce-mri
#3
Yuan Le, Marcel Dominik Nickel, Stephan Kannengiesser, Berthold Kiefer, Bruce Spottiswoode, Brian Dale, Victor Soon, Chen Lin
OBJECTIVE: To develop a novel framework for evaluating the accuracy of quantitative analysis on dynamic contrast-enhanced (DCE) MRI with a specific combination of imaging technique, scanning parameters, and scanner and software performance and to test this framework with breast DCE MRI with Time-resolved angiography WIth Stochastic Trajectories (TWIST). MATERIALS AND METHODS: Realistic breast tumor phantoms were 3D printed as cavities and filled with solutions of MR contrast agent...
September 11, 2017: Magma
https://www.readbyqxmd.com/read/28884314/spectroscopic-sampling-of-the-left-side-of-long-te-spin-echoes-a-free-lunch
#4
Robert V Mulkern, Mukund Balasubramanian
OBJECTIVE: Use of spectroscopically-acquired spin echoes typically involves Fourier transformation of the right side of the echo while largely neglecting the left side. For sufficiently long echo times, the left side may have enough spectral resolution to offer some utility. Since the acquisition of this side is "free", we deemed it worthy of attention and investigated the spectral properties and information content of this data. MATERIALS AND METHODS: Theoretical expressions for left- and right-side spectra were derived assuming Lorentzian frequency distributions...
September 7, 2017: Magma
https://www.readbyqxmd.com/read/28808823/vessel-wall-characterization-using-quantitative-mri-what-s-in-a-number
#5
REVIEW
Bram F Coolen, Claudia Calcagno, Pim van Ooij, Zahi A Fayad, Gustav J Strijkers, Aart J Nederveen
The past decade has witnessed the rapid development of new MRI technology for vessel wall imaging. Today, with advances in MRI hardware and pulse sequences, quantitative MRI of the vessel wall represents a real alternative to conventional qualitative imaging, which is hindered by significant intra- and inter-observer variability. Quantitative MRI can measure several important morphological and functional characteristics of the vessel wall. This review provides a detailed introduction to novel quantitative MRI methods for measuring vessel wall dimensions, plaque composition and permeability, endothelial shear stress and wall stiffness...
August 14, 2017: Magma
https://www.readbyqxmd.com/read/28785850/highly-accelerated-intracranial-4d-flow-mri-evaluation-of-healthy-volunteers-and-patients-with-intracranial-aneurysms
#6
Jing Liu, Louise Koskas, Farshid Faraji, Evan Kao, Yan Wang, Henrik Haraldsson, Sarah Kefayati, Chengcheng Zhu, Sinyeob Ahn, Gerhard Laub, David Saloner
OBJECTIVES: To evaluate an accelerated 4D flow MRI method that provides high temporal resolution in a clinically feasible acquisition time for intracranial velocity imaging. MATERIALS AND METHODS: Accelerated 4D flow MRI was developed by using a pseudo-random variable-density Cartesian undersampling strategy (CIRCUS) with the combination of k-t, parallel imaging and compressed sensing image reconstruction techniques (k-t SPARSE-SENSE). Four-dimensional flow data were acquired on five healthy volunteers and eight patients with intracranial aneurysms using CIRCUS (acceleration factor of R = 4, termed CIRCUS4) and GRAPPA (R = 2, termed GRAPPA2) as the reference method...
August 7, 2017: Magma
https://www.readbyqxmd.com/read/28770356/radial-mri-with-variable-echo-times-reducing-the-orientation-dependency-of-susceptibility-artifacts-of-an-mr-safe-guidewire
#7
Katharina E Schleicher, Michael Bock, Klaus Düring, Stefan Kroboth, Axel J Krafft
OBJECTIVES: Guidewires are indispensable tools for intravascular MR-guided interventions. Recently, an MR-safe guidewire made from a glass-fiber/epoxy compound material with embedded iron particles was developed. The size of the induced susceptibility artifact, and thus the guidewire's visibility, depends on its orientation against B 0. We present a radial acquisition scheme with variable echo times that aims to reduce the artifact's orientation dependency. MATERIALS AND METHODS: The radial acquisition scheme uses sine-squared modulated echo times depending on the physical direction of the spoke to balance the susceptibility artifact of the guidewire...
August 2, 2017: Magma
https://www.readbyqxmd.com/read/28744673/utilization-of-mr-angiography-in-perfusion-imaging-for-identifying-arterial-input-function
#8
Bora Buyuksarac, Mehmed Ozkan
OBJECTIVE: This research utilizes magnetic resonance angiography (MRA) to identify arterial locations during the parametric evaluation of concentration time curves (CTCs), and to prevent shape distortions in arterial input function (AIF). MATERIALS AND METHODS: We carried out cluster analysis with the CTC parameters of voxels located within and around the middle cerebral artery (MCA). Through MRA, we located voxels that meet the AIF criteria and those with distorted CTCs...
July 25, 2017: Magma
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
#9
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
#10
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
#11
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/28332039/combined-quantification-of-fatty-infiltration-t-1-relaxation-times-and-t-2-relaxation-times-in-normal-appearing-skeletal-muscle-of-controls-and-dystrophic-patients
#12
Benjamin Leporq, Arnaud Le Troter, Yann Le Fur, Emmanuelle Salort-Campana, Maxime Guye, Olivier Beuf, Shahram Attarian, David Bendahan
OBJECTIVES: To evaluate the combination of a fat-water separation method with an automated segmentation algorithm to quantify the intermuscular fatty-infiltrated fraction, the relaxation times, and the microscopic fatty infiltration in the normal-appearing muscle. MATERIALS AND METHODS: MR acquisitions were performed at 1.5T in seven patients with facio-scapulo-humeral dystrophy and eight controls. Disease severity was assessed using commonly used scales for the upper and lower limbs...
August 2017: Magma
https://www.readbyqxmd.com/read/28321524/what-are-the-true-volumes-of-sega-tumors-reliability-of-planimetric-and-popular-semi-automated-image-segmentation-methods
#13
Konrad Stawiski, Joanna Trelińska, Dobromiła Baranska, Iwona Dachowska, Katarzyna Kotulska, Sergiusz Jóźwiak, Wojciech Fendler, Wojciech Młynarski
OBJECTIVE: To evaluate the reliability of the standard planimetric methodology of volumetric analysis and three different open-source semi-automated approaches of brain tumor segmentation. MATERIALS AND METHODS: The volumes of subependymal giant cell astrocytomas (SEGA) examined by 30 MRI studies of 10 patients from a previous everolimus-related trial (EMINENTS study) were estimated using four methods: planimetric method (modified MacDonald ellipsoid method), ITK-Snap (pixel clustering, geodesic active contours, region competition methods), 3D Slicer (level-set thresholding), and NIRFast (k-means clustering, Markov random fields)...
August 2017: Magma
https://www.readbyqxmd.com/read/28283853/long-t2-suppression-in-native-lung-3-d-imaging-using-k-space-reordered-inversion-recovery-dual-echo-ultrashort-echo-time-mri
#14
Neville D Gai, Ashkan A Malayeri, David A Bluemke
OBJECTIVE: Long T2 species can interfere with visualization of short T2 tissue imaging. For example, visualization of lung parenchyma can be hindered by breathing artifacts primarily from fat in the chest wall. The purpose of this work was to design and evaluate a scheme for long T2 species suppression in lung parenchyma imaging using 3-D inversion recovery double-echo ultrashort echo time imaging with a k-space reordering scheme for artifact suppression. MATERIALS AND METHODS: A hyperbolic secant (HS) pulse was evaluated for different tissues (T1/T2)...
August 2017: Magma
https://www.readbyqxmd.com/read/28265814/a-comparative-study-of-the-sensitivity-of-diffusion-related-parameters-obtained-from-diffusion-tensor-imaging-diffusional-kurtosis-imaging-q-space-analysis-and-bi-exponential-modelling-in-the-early-disease-course-24%C3%A2-h-of-hyperacute-6%C3%A2-h-ischemic-stroke-patients
#15
Gaëtan Duchêne, Frank Peeters, André Peeters, Thierry Duprez
OBJECTIVES: To compare the sensitivity and early temporal changes of diffusion parameters obtained from diffusion tensor imaging (DTI), diffusional kurtosis imaging (DKI), q-space analysis (QSA) and bi-exponential modelling in hyperacute stroke patients. MATERIALS AND METHODS: A single investigational acquisition allowing the four diffusion analyses was performed on seven hyperacute stroke patients with a 3T system. The percentage change between ipsi- and contralateral regions were compared at admission and 24 h later...
August 2017: Magma
https://www.readbyqxmd.com/read/28246950/biomarkers-from-in-vivo-molecular-imaging-of-breast-cancer-pretreatment-18-f-fdg-pet-predicts-patient-prognosis-and-pretreatment-dwi-mr-predicts-response-to-neoadjuvant-chemotherapy
#16
Francesca Gallivanone, Marta Maria Panzeri, Carla Canevari, Claudio Losio, Luigi Gianolli, Francesco De Cobelli, Isabella Castiglioni
OBJECTIVE: Human cancers display intra-tumor phenotypic heterogeneity and recent research has focused on developing image processing methods extracting imaging descriptors to characterize this heterogeneity. This work assesses the role of pretreatment (18)F-FDG PET and DWI-MR with respect to the prognosis and prediction of neoadjuvant chemotherapy (NAC) outcomes when image features are used to characterize primitive lesions from breast cancer (BC). MATERIALS AND METHODS: A retrospective protocol included 38 adult women with biopsy-proven BC...
August 2017: Magma
https://www.readbyqxmd.com/read/28220266/interpretation-of-cardiac-wall-motion-from-cine-mri-combined-with-parametric-imaging-based-on-the-hilbert-transform
#17
Narjes Benameur, Enrico Gianluca Caiani, Younes Arous, Nejmeddine Ben Abdallah, Tarek Kraiem
OBJECT: The aim of this study was to test and validate the clinical impact of parametric amplitude images obtained using the Hilbert transform on the regional interpretation of cardiac wall motion abnormalities from cine-MR images by non-expert radiologists compared with expert consensus. MATERIALS AND METHODS: Cine-MRI short-axis images obtained in 20 patients (10 with myocardial infarction, 5 with myocarditis and 5 with normal function) were processed to compute a parametric amplitude image for each using the Hilbert transform...
August 2017: Magma
https://www.readbyqxmd.com/read/28181027/track-weighted-imaging-methods-extracting-information-from-a-streamlines-tractogram
#18
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...
August 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
#19
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)...
August 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
#20
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
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