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Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine

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https://www.readbyqxmd.com/read/29687927/diffusion-weighted-magnetic-resonance-spectroscopy-boosted-by-simultaneously-acquired-water-reference-signals
#1
André Döring, Victor Adalid, Chris Boesch, Roland Kreis
PURPOSE: To combine the metabolite-cycling technique with diffusion-weighted 1 H-MR spectroscopy and to use the inherent water reference for compensation of motion-related signal loss for improved estimation of metabolite apparent diffusion coefficients (ADCs). METHODS: Diffusion-weighted spectra of water and metabolites were acquired simultaneously using metabolite-cycling at 3 T. The water information was used for signal correction of phase, frequency, and eddy currents, as well as for compensation of motion-induced signal loss...
April 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29687923/quantitative-susceptibility-mapping-of-articular-cartilage-ex-vivo-findings-at-multiple-orientations-and-following-different-degradation-treatments
#2
Olli Nykänen, Lassi Rieppo, Juha Töyräs, Ville Kolehmainen, Simo Saarakkala, Karin Shmueli, Mikko J Nissi
PURPOSE: We investigated the feasibility of quantitative susceptibility mapping (QSM) for assessing degradation of articular cartilage by measuring ex vivo bovine cartilage samples subjected to different degradative treatments. Specimens were scanned at several orientations to study if degradation affects the susceptibility anisotropy. T2*-mapping, histological stainings, and polarized light microscopy were used as reference methods. Additionally, simulations of susceptibility in layered geometry were performed...
April 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29687921/t1-weighted-fat-water-separated-propeller-acquired-with-dual-bandwidths
#3
Henric Rydén, Johan Berglund, Ola Norbeck, Enrico Avventi, Stefan Skare
PURPOSE: To describe a fat/water separated dual receiver bandwidth (rBW) spin echo PROPELLER sequence that eliminates the dead time associated with single rBW sequences. A nonuniform noise whitening by regularization of the fat/water inverse problem is proposed, to enable dual rBW reconstructions. METHODS: Bipolar, flyback, and dual spin echo sequences were developed. All sequences acquire two echoes with different rBW without dead time. Chemical shift displacement was corrected by performing the fat/water separation in k-space, prior to gridding...
April 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29687919/controlling-motion-artefact-levels-in-mr-images-by-suspending-data-acquisition-during-periods-of-head-motion
#4
Rémi Castella, Lionel Arn, Estelle Dupuis, Martina F Callaghan, Bogdan Draganski, Antoine Lutti
PURPOSE: Head movements are a major source of MRI artefacts. Prospective motion correction techniques significantly improve data quality, but strong motion artefacts may remain in the data. We introduce a framework to suspend data acquisition during periods of head motion over a predefined threshold. METHODS: Data was acquired with prospective motion correction and an external optical tracking system. A predictor of motion impact was introduced that accounts for the amplitude of the signal acquired at the time of the motion...
April 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29687916/mri-based-wireless-determination-of-the-transfer-function-of-a-linear-implant-introduction-of-the-transfer-matrix
#5
Janot P Tokaya, Alexander J E Raaijmakers, Peter R Luijten, Cornelis A T van den Berg
PURPOSE: We introduce the transfer matrix (TM) that makes MR-based wireless determination of transfer functions (TFs) possible. TFs are implant specific measures for RF-safety assessment of linear implants. The TF relates an incident tangential electric field on an implant to a scattered electric field at its tip that generally governs local heating. The TM extends this concept and relates an incident tangential electric field to a current distribution in the implant therewith characterizing the RF response along the entire implant...
April 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29687915/single-shot-t-2-mapping-using-overlapping-echo-detachment-planar-imaging-and-a-deep-convolutional-neural-network
#6
Congbo Cai, Chao Wang, Yiqing Zeng, Shuhui Cai, Dong Liang, Yawen Wu, Zhong Chen, Xinghao Ding, Jianhui Zhong
PURPOSE: An end-to-end deep convolutional neural network (CNN) based on deep residual network (ResNet) was proposed to efficiently reconstruct reliable T2 mapping from single-shot overlapping-echo detachment (OLED) planar imaging. METHODS: The training dataset was obtained from simulations that were carried out on SPROM (Simulation with PRoduct Operator Matrix) software developed by our group. The relationship between the original OLED image containing two echo signals and the corresponding T2 mapping was learned by ResNet training...
April 24, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29682800/an-analytic-expression-for-the-ultimate-intrinsic-snr-in-a-uniform-sphere
#7
Hong-Hsi Lee, Daniel K Sodickson, Riccardo Lattanzi
PURPOSE: The ultimate intrinsic signal-to-noise ratio (UISNR) is normally calculated using electrodynamic simulations with a complete basis of modes. Here, we provide an exact solution for the UISNR at the center of a dielectric sphere and assess how accurately this solution approximates UISNR away from the center. METHODS: We performed a mode analysis to determine which modes contribute to central UISNR - ζ(r→0). We then derived an analytic expression to calculate ζ(r→0) and analyzed its dependence on main magnetic field strength, sample geometry, and electrical properties...
April 22, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29682792/rapid-assessment-of-pulmonary-gas-transport-with-hyperpolarized-129xe-mri-using-a-3d-radial-double-golden-means-acquisition-with-variable-flip-angles
#8
Kai Ruppert, Faraz Amzajerdian, Hooman Hamedani, Yi Xin, Luis Loza, Tahmina Achekzai, Ian F Duncan, Harrilla Profka, Sarmad Siddiqui, Mehrdad Pourfathi, Maurizio F Cereda, Stephen Kadlecek, Rahim R Rizi
PURPOSE: To demonstrate the feasibility of using a 3D radial double golden-means acquisition with variable flip angles to monitor pulmonary gas transport in a single breath hold with hyperpolarized xenon-129 MRI. METHODS: Hyperpolarized xenon-129 MRI scans with interleaved gas-phase and dissolved-phase excitations were performed using a 3D radial double golden-means acquisition in mechanically ventilated rabbits. The flip angle was either held fixed at 15 ° or 5 °, or it was varied linearly in ascending or descending order between 5 ° and 15 ° over a sampling interval of 1000 spokes...
April 22, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29682783/optimized-respiratory-resolved-motion-compensated-3d-cartesian-coronary-mr-angiography
#9
Teresa Correia, Giulia Ginami, Gastão Cruz, Radhouene Neji, Imran Rashid, René M Botnar, Claudia Prieto
PURPOSE: To develop a robust and efficient reconstruction framework that provides high-quality motion-compensated respiratory-resolved images from free-breathing 3D whole-heart Cartesian coronary magnetic resonance angiography (CMRA) acquisitions. METHODS: Recently, XD-GRASP (eXtra-Dimensional Golden-angle RAdial Sparse Parallel MRI) was proposed to achieve 100% scan efficiency and provide respiratory-resolved 3D radial CMRA images by exploiting sparsity in the respiratory dimension...
April 22, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29672922/myocardial-perfusion-quantification-using-simultaneously-acquired-13-nh-3-ammonia-pet-and-dynamic-contrast-enhanced-mri-in-patients-at-rest-and-stress
#10
Karl P Kunze, Stephan G Nekolla, Christoph Rischpler, Shelley HuaLei Zhang, Carmel Hayes, Nicolas Langwieser, Tareq Ibrahim, Karl-Ludwig Laugwitz, Markus Schwaiger
PURPOSE: Systematic differences with respect to myocardial perfusion quantification exist between DCE-MRI and PET. Using the potential of integrated PET/MRI, this study was conceived to compare perfusion quantification on the basis of simultaneously acquired 13 NH3 -ammonia PET and DCE-MRI data in patients at rest and stress. METHODS: Twenty-nine patients were examined on a 3T PET/MRI scanner. DCE-MRI was implemented in dual-sequence design and additional T1 mapping for signal normalization...
April 19, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29672917/a-joint-space-angle-regularization-approach-for-single-4d-diffusion-image-super-resolution
#11
Shi Yin, Xinge You, Xin Yang, Qinmu Peng, Ziqi Zhu, Xiao-Yuan Jing
PURPOSE: Low signal-to-noise-ratio and limited scan time of diffusion magnetic resonance imaging (dMRI) in current clinical settings impede obtaining images with high spatial and angular resolution (HSAR) for a reliable fiber reconstruction with fine anatomical details. To overcome this problem, we propose a joint space-angle regularization approach to reconstruct HSAR diffusion signals from a single 4D low resolution (LR) dMRI, which is down-sampled in both 3D-space and q-space. METHODS: Different from the existing works which combine multiple 4D LR diffusion images acquired using specific acquisition protocols, the proposed method reconstructs HSAR dMRI from only a single 4D dMRI by exploring and integrating two key priors, that is, the nonlocal self-similarity in the spatial domain as a prior to increase spatial resolution and ridgelet approximations in the diffusion domain as another prior to increase the angular resolution of dMRI...
April 19, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29663507/grappa-reconstructed-wave-caipi-mp-rage-at-7-tesla
#12
Jolanda M Schwarz, Eberhard D Pracht, Daniel Brenner, Martin Reuter, Tony Stöcker
PURPOSE: The aim of this project was to develop a GRAPPA-based reconstruction for wave-CAIPI data. Wave-CAIPI fully exploits the 3D coil sensitivity variations by combining corkscrew k-space trajectories with CAIPIRINHA sampling. It reduces artifacts and limits reconstruction induced spatially varying noise enhancement. The GRAPPA-based wave-CAIPI method is robust and does not depend on the accuracy of coil sensitivity estimations. METHODS: We developed a GRAPPA-based, noniterative wave-CAIPI reconstruction algorithm utilizing multiple GRAPPA kernels...
April 16, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29656522/hybrid-t-2-and-t-1-weighted-radial-acquisition-for-free-breathing-abdominal-examination
#13
Thomas Benkert, John P Mugler, David S Rigie, Daniel K Sodickson, Hersh Chandarana, Kai Tobias Block
PURPOSE: Most clinical MR examinations require acquisition of different image contrasts. For abdominal exams, the scans are conventionally performed as separate acquisitions using respiratory gating or repeated breath holding, which can be time-inefficient and challenging for patients. Here, a hybrid imaging approach is described that creates T2 - and T1 -weighted images from a single scan and allows for free-breathing acquisition. THEORY AND METHODS: T2 -weighted data is collected using 3D fast spin-echo (FSE) acquisition with motion-robust radial stack-of-stars sampling...
April 15, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29656510/robust-motion-correction-in-cest-imaging-exploiting-low-rank-approximation-of-the-z-spectrum
#14
Tobias Wech, Herbert Köstler
PURPOSE: To introduce and evaluate an image registration technique for robust quantification of CEST acquisitions corrupted by motion. METHODS: The proposed iterative algorithm exploits a low-rank approximation of the z-spectrum (LRAZ), to gradually separate the contrast variation due to saturation at different off-resonance frequencies and accompanying motion. This registration method was first tested in a creatine CEST analysis of a phantom with simulated rigid motion...
April 15, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29656481/toward-in-vivo-quantification-of-induced-rf-currents-on-long-thin-conductors
#15
Gregory H Griffin, Venkat Ramanan, Jennifer Barry, Graham A Wright
PURPOSE: Most MR-guided catheter-based procedures, and imaging of patients with implanted medical devices, are currently contraindicated due to a significant risk of heating associated with induced RF currents. The induced RF current produces a corresponding artifact which can be used to remotely characterize current and safely predict RF heating. Application of this remote technique in vivo to safely quantify RF heating risk may allow for execution of many scans currently contraindicated...
April 15, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29656446/hemodynamic-response-function-hrf-variability-confounds-resting-state-fmri-functional-connectivity
#16
D Rangaprakash, Guo-Rong Wu, Daniele Marinazzo, Xiaoping Hu, Gopikrishna Deshpande
PURPOSE: fMRI is the convolution of the hemodynamic response function (HRF) and unmeasured neural activity. HRF variability (HRFv) across the brain could, in principle, alter functional connectivity (FC) estimates from resting-state fMRI (rs-fMRI). Given that HRFv is driven by both neural and non-neural factors, it is problematic when it confounds FC. However, this aspect has remained largely unexplored even though FC studies have grown exponentially. We hypothesized that HRFv confounds FC estimates in the brain's default-mode-network...
April 15, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29656440/in-plane-superresolution-mri-with-phaseless-sub-pixel-encoding
#17
Franciszek Hennel, Rui Tian, Maria Engel, Klaas P Pruessmann
PURPOSE: Acquisition of high-resolution imaging data using multiple excitations without the sensitivity to fluctuations of the transverse magnetization phase, which is a major problem of multi-shot MRI. THEORY AND METHODS: The concept of superresolution MRI based on microscopic tagging is analyzed using an analogy with the optical method of structured illumination. Sinusoidal tagging is shown to provide subpixel resolution by mixing of neighboring spatial frequency (k-space) bands...
April 15, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29656389/the-robustness-of-t-2-value-as-a-trabecular-structural-index-at-multiple-spatial-resolutions-of-7-tesla-mri
#18
D K Lee, Y K Song, B W Park, H P Cho, J S Yeom, G Cho, H Cho
PURPOSE: To evaluate the robustness of MR transverse relaxation times of trabecular bone from spin-echo and gradient-echo acquisitions at multiple spatial resolutions of 7 T. METHODS: The effects of MRI resolutions to T2 and T2* of trabecular bone were numerically evaluated by Monte Carlo simulations. T2 , T2*, and trabecular structural indices from multislice multi-echo and UTE acquisitions were measured in defatted human distal femoral condyles on a 7 T scanner...
April 15, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29626359/simultaneous-ph-sensitive-and-oxygen-sensitive-mri-of-human-gliomas-at-3-t-using-multi-echo-amine-proton-chemical-exchange-saturation-transfer-spin-and-gradient-echo-echo-planar-imaging-cest-sage-epi
#19
Robert J Harris, Jingwen Yao, Ararat Chakhoyan, Catalina Raymond, Kevin Leu, Linda M Liau, Phioanh L Nghiemphu, Albert Lai, Noriko Salamon, Whitney B Pope, Timothy F Cloughesy, Benjamin M Ellingson
PURPOSE: To introduce a new pH-sensitive and oxygen-sensitive MRI technique using amine proton CEST echo spin-and-gradient echo (SAGE) EPI (CEST-SAGE-EPI). METHODS: pH-weighting was obtained using CEST estimations of magnetization transfer ratio asymmetry (MTRasym ) at 3 ppm, and oxygen-weighting was obtained using R2' measurements. Glutamine concentration, pH, and relaxation rates were varied in phantoms to validate simulations and estimate relaxation rates. The values of MTRasym and R2' in normal-appearing white matter, T2 hyperintensity, contrast enhancement, and macroscopic necrosis were measured in 47 gliomas...
April 6, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29624736/mr-fingerprinting-deep-reconstruction-network-drone
#20
Ouri Cohen, Bo Zhu, Matthew S Rosen
PURPOSE: Demonstrate a novel fast method for reconstruction of multi-dimensional MR fingerprinting (MRF) data using deep learning methods. METHODS: A neural network (NN) is defined using the TensorFlow framework and trained on simulated MRF data computed with the extended phase graph formalism. The NN reconstruction accuracy for noiseless and noisy data is compared to conventional MRF template matching as a function of training data size and is quantified in simulated numerical brain phantom data and International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom data measured on 1...
April 6, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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