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David Norris
No abstract text is available yet for this article.
January 8, 2018: Magma
Rita G Nunes, Joseph V Hajnal
OBJECTIVE: Point spread function (PSF) mapping enables estimating the displacement fields required for distortion correction of echo planar images. Recently, a highly accelerated approach was introduced for estimating displacements from the phase slope of under-sampled PSF mapping data. Sampling schemes with varying spacing were proposed requiring stepwise phase unwrapping. To avoid unwrapping errors, an alternative approach applying the concept of finite rate of innovation to PSF mapping (FRIP) is introduced, using a pattern search strategy to locate the PSF peak, and the two methods are compared...
January 3, 2018: Magma
Xin Zhang, Xiangyang Zhu, Christopher Martyn Ferguson, Kai Jiang, Tyson Burningham, Amir Lerman, Lilach Orly Lerman
OBJECTIVE: Low-energy shockwave (SW) therapy attenuates damage in the stenotic kidney (STK) caused by atherosclerotic renal artery stenosis (ARAS). We hypothesized that magnetic resonance elastography (MRE) would detect attenuation of fibrosis following SW in unilateral ARAS kidneys. MATERIALS AND METHODS: Domestic pigs were randomized to control, unilateral ARAS, and ARAS treated with 6 sessions of SW over 3 consecutive weeks (n = 7 each) starting after 3 weeks of ARAS or sham...
December 30, 2017: Magma
Shuo Zhang, Thu Thao Le, Sven Kabus, Boyang Su, Derek J Hausenloy, Stuart A Cook, Calvin W L Chin, Ru San Tan
OBJECTIVE: Our aim was to investigate the technical feasibility of a novel motion compensation method for cardiac magntic resonance (MR) T1 and extracellular volume fraction (ECV) mapping. MATERIALS AND METHODS: Native and post-contrast T1 maps were obtained using modified look-locker inversion recovery (MOLLI) pulse sequences with acquisition scheme defined in seconds. A nonrigid, nonparametric, fast elastic registration method was applied to generate motion-corrected T1 maps and subsequently ECV maps...
December 21, 2017: Magma
Elias Kellner, Irina Mader, Marco Reisert, Horst Urbach, Valerij Gennadevic Kiselev
OBJECT: We aimed to modify our previously published method for arterial input function measurements for evaluation of cerebral perfusion (dynamic susceptibility contrast MRI) such that it can be applied in humans in a clinical setting. MATERIALS AND METHODS: Similarly to our previous work, a conventional measurement sequence for dynamic susceptibility contrast MRI is extended with an additional measurement slice at the neck. Measurement parameters at this slice were optimized for the blood signal (short echo time, background suppression, magnitude and phase images)...
December 9, 2017: Magma
Haining Liu, Gregory J Wilson, Niranjan Balu, Jeffrey H Maki, Daniel S Hippe, Wei Wu, Hiroko Watase, Jinnan Wang, Martin L Gunn, Chun Yuan
OBJECTIVES: A postprocessing technique termed 3D true-phase polarity recovery with independent phase estimation using three-tier stacks based region growing (3D-TRIPS) was developed, which directly reconstructs phase-sensitive inversion-recovery images without acquisition of phase-reference images. The utility of this technique is demonstrated in myocardial late gadolinium enhancement (LGE) imaging. MATERIALS AND METHODS: A data structure with three tiers of stacks was used for 3D-TRIPS to directly achieve reliable region growing for successful background-phase estimation...
December 7, 2017: Magma
Chengcheng Zhu, Bing Tian, Luguang Chen, Laura Eisenmenger, Esther Raithel, Christoph Forman, Sinyeob Ahn, Gerhard Laub, Qi Liu, Jianping Lu, Jing Liu, Christopher Hess, David Saloner
OBJECTIVE: Develop and optimize an accelerated, high-resolution (0.5 mm isotropic) 3D black blood MRI technique to reduce scan time for whole-brain intracranial vessel wall imaging. MATERIALS AND METHODS: A 3D accelerated T1-weighted fast-spin-echo prototype sequence using compressed sensing (CS-SPACE) was developed at 3T. Both the acquisition [echo train length (ETL), under-sampling factor] and reconstruction parameters (regularization parameter, number of iterations) were first optimized in 5 healthy volunteers...
December 5, 2017: Magma
Bart R Steensma, Ingmar J Voogt, Tim Leiner, Peter R Luijten, Jesse Habets, Dennis W J Klomp, Cornelis A T van den Berg, Alexander J E Raaijmakers
OBJECTIVE: To demonstrate imaging performance for cardiac MR imaging at 7 T using a coil array of 8 transmit/receive dipole antennas and 16 receive loops. MATERIALS AND METHODS: An 8-channel dipole array was extended by adding 16 receive-only loops. Average power constraints were determined by electromagnetic simulations. Cine imaging was performed on eight healthy subjects. Geometrical factor (g-factor) maps were calculated to assess acceleration performance. Signal-to-noise ratio (SNR)-scaled images were reconstructed for different combinations of receive channels, to demonstrate the SNR benefits of combining loops and dipoles...
November 24, 2017: Magma
Oliver Gloger, Robin Bülow, Klaus Tönnies, Henry Völzke
OBJECTIVES: We aimed to develop the first fully automated 3D gallbladder segmentation approach to perform volumetric analysis in volume data of magnetic resonance (MR) cholangiopancreatography (MRCP) sequences. Volumetric gallbladder analysis is performed for non-contrast-enhanced and secretin-enhanced MRCP sequences. MATERIALS AND METHODS: Native and secretin-enhanced MRCP volume data were produced with a 1.5-T MR system. Images of coronal maximum intensity projections (MIP) are used to automatically compute 2D characteristic shape features of the gallbladder in the MIP images...
November 24, 2017: Magma
Patrick J Cozzone
No abstract text is available yet for this article.
November 17, 2017: Magma
Marius Menza, Daniela Föll, Jürgen Hennig, Bernd Jung
OBJECTIVE: Myocardial dysfunction of the right ventricle (RV) is an important indicator of RV diseases, e.g. RV infarction or pulmonary hypertension. Tissue phase mapping (TPM) has been widely used to determine function of the left ventricle (LV) by analyzing myocardial velocities. The analysis of RV motion is more complicated due to the different geometry and smaller wall thickness. The aim of this work was to adapt and optimize TPM to the demands of the RV. MATERIALS AND METHODS: TPM measurements were acquired in 25 healthy volunteers using a velocity-encoded phase-contrast sequence and kt-accelerated parallel imaging in combination with optimized navigator strategy and blood saturation...
November 15, 2017: Magma
Peter T While, Jose R Teruel, Igor Vidić, Tone F Bathen, Pål Erik Goa
OBJECTIVE: To explore the relationship between relative enhanced diffusivity (RED) and intravoxel incoherent motion (IVIM), as well as the impact of noise and the choice of intermediate diffusion weighting (b value) on the RED parameter. MATERIALS AND METHODS: A mathematical derivation was performed to cast RED in terms of the IVIM parameters. Noise analysis and b value optimization was conducted by using Monte Carlo calculations to generate diffusion-weighted imaging data appropriate to breast and liver tissue at three different signal-to-noise ratios...
November 6, 2017: Magma
Manushka V Vaidya, Cem M Deniz, Christopher M Collins, Daniel K Sodickson, Riccardo Lattanzi
OBJECTIVE: To use high-permittivity materials (HPM) positioned near radiofrequency (RF) surface coils to manipulate transmit/receive field patterns. MATERIALS AND METHODS: A large HPM pad was placed below the RF coil to extend the field of view (FOV). The resulting signal-to-noise ratio (SNR) was compared with that of other coil configurations covering the same FOV in simulations and experiments at 7 T. Transmit/receive efficiency was evaluated when HPM discs with or without a partial shield were positioned at a distance from the coil...
November 6, 2017: Magma
Jolanda M Spijkerman, Esben T Petersen, Jeroen Hendrikse, Peter Luijten, Jaco J M Zwanenburg
OBJECT: Cerebrospinal fluid (CSF) T 2 mapping can potentially be used to investigate CSF composition. A previously proposed CSF T 2-mapping method reported a T 2 difference between peripheral and ventricular CSF, and suggested that this reflected different CSF compositions. We studied the performance of this method at 7 T and evaluated the influence of partial volume and B 1 and B 0 inhomogeneity. MATERIALS AND METHODS: T 2-preparation-based CSF T 2-mapping was performed in seven healthy volunteers at 7 and 3 T, and was compared with a single echo spin-echo sequence with various echo times...
November 6, 2017: Magma
Emma M Meeus, Jan Novak, Hamid Dehghani, Andrew C Peet
OBJECTIVE: This study aimed to investigate the reliability of intravoxel incoherent motion (IVIM) model derived parameters D and f and their dependence on b value distributions with a rapid three b value acquisition protocol. MATERIALS AND METHODS: Diffusion models for brain, kidney, and liver were assessed for bias, error, and reproducibility for the estimated IVIM parameters using b values 0 and 1000, and a b value between 200 and 900, at signal-to-noise ratios (SNR) 40, 55, and 80...
October 26, 2017: Magma
Eve Piekarski, Teodora Chitiboi, Rebecca Ramb, Larry A Latson, Puneet Bhatla, Li Feng, Leon Axel
OBJECTIVES: Residual respiratory motion degrades image quality in conventional cardiac cine MRI (CCMRI). We evaluated whether a free-breathing (FB) radial imaging CCMRI sequence with compressed sensing reconstruction [extradimensional (e.g. cardiac and respiratory phases) golden-angle radial sparse parallel, or XD-GRASP] could provide better image quality than a conventional Cartesian breath-held (BH) sequence in an unselected population of patients undergoing clinical CCMRI. MATERIALS AND METHODS: One hundred one patients who underwent BH and FB imaging in a midventricular short-axis plane at a matching location were included...
October 24, 2017: Magma
Florian Siedek, Thorsten Persigehl, Roman-Ulrich Mueller, Volker Burst, Thomas Benzing, David Maintz, Stefan Haneder
OBJECTIVE: Acute kidney injury (AKI) is an important risk factor for a number of adverse outcomes including end-stage renal disease and cardiovascular morbidity and mortality. Whilst many clinical situations that can induce AKI are known-e.g. drug toxicity, contrast agent exposure or ischemia during surgery-targeted preventive or therapeutic measures are still lacking. As to renoprotective strategies, remote ischemic preconditioning (RIPC) is one of the most promising novel approaches and has been examined by a number of clinical trials...
October 23, 2017: Magma
Ana Francisca Soares, João M N Duarte, Rolf Gruetter
OBJECTIVE: We monitored hepatic lipid content (HLC) and fatty acid (FA) composition in the context of enhanced lipid handling induced by a metabolic high-fat diet (HFD) challenge and fasting. MATERIALS AND METHODS: Mice received a control diet (10% of kilocalories from fat, N = 14) or an HFD (45% or 60% of kilocalories from fat, N = 10 and N = 16, respectively) for 26 weeks. A subset of five mice receiving an HFD (60% of kilocalories from fat) were switched to the control diet for the final 7 weeks...
October 12, 2017: Magma
(no author information available yet)
No abstract text is available yet for this article.
October 2017: Magma
(no author information available yet)
No abstract text is available yet for this article.
October 2017: Magma
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