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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/30515876/data-consistency-driven-determination-of-b-0-fluctuations-in-gradient-echo-mri
#1
Jakob Meineke, Tim Nielsen
PURPOSE: Introduce a method to estimate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>B</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:math> -fluctuations based on the analysis of raw k-space data, without sequence modifications or external hardware, and correct for their detrimental effects in gradient-echo MRI. THEORY: Inconsistencies in multi-channel raw k-space data can be used to estimate <mml:math xmlns:mml="http://www...
December 4, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30515853/accelerated-imaging-of-metallic-implants-using-model-based-nonlinear-reconstruction
#2
Xinwei Shi, Evan Levine, Hans Weber, Brian A Hargreaves
PURPOSE: To accelerate imaging near metallic implants with multi-spectral imaging (MSI) techniques by exploiting a signal model in the spectral dimension. METHODS: MSI techniques resolve metal-induced field perturbations by acquiring separate 3D spatial encodings at multiple excitation frequencies, which are referred to as spectral bins. The proposed model-based reconstruction exploits the correlation between spectral bins in image reconstruction by enforcing a signal model to describe the signal profile across bins...
December 4, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30515852/comparison-of-in-vivo-lung-morphometry-models-from-3d-multiple-b-value-3-he-and-129-xe-diffusion-weighted-mri
#3
Ho-Fung Chan, Guilhem J Collier, Nicholas D Weatherley, Jim M Wild
PURPOSE: To compare in vivo lung morphometry parameters derived from theoretical gas diffusion models, the cylinder model and stretched exponential model, in a range of acinar microstructural length scales encountered in healthy and diseased lungs with 3 He and 129 Xe diffusion-weighted MRI. METHODS: Three-dimensional multiple b-value 3 He and 129 Xe diffusion-weighted MRI was acquired with compressed sensing at 1.5 T from 51 and 31 subjects, respectively, including healthy volunteers, ex-smokers, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease patients...
December 4, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506959/measuring-intra-axonal-t-2-in-white-matter-with-direction-averaged-diffusion-mri
#4
Emilie T McKinnon, Jens H Jensen
PURPOSE: To demonstrate how the T2 relaxation time of intra-axonal water (T2a ) in white matter can be measured with direction-averaged diffusion MRI. METHODS: For b-values larger than about 4000 s/mm2 , the direction-averaged diffusion MRI signal from white matter is dominated by the contribution from water within axons, which enables T2a to be estimated by acquiring data for multiple TE values and fitting a mono-exponential decay curve. If given a value of the intra-axonal diffusivity, an extension of the method allows the extra-axonal relaxation time (T2e ) to be calculated also...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506957/acceleration-of-vessel-selective-dynamic-mr-angiography-by-pseudocontinuous-arterial-spin-labeling-in-combination-with-acquisition-of-control-and-labeled-images-in-the-same-shot-actress
#5
Yuriko Suzuki, Thomas W Okell, Noriyuki Fujima, Matthias J P van Osch
PURPOSE: The recently introduced "Acquisition of ConTRol and labEled imaging in the Same Shot" (ACTRESS) approach was designed to halve the scan time of arterial spin labeling (ASL) -based 4D-MRA by obtaining both labeled and control images in a single Look-Locker readout. However, application for vessel-selective labeling remains difficult. The aim of this study was to achieve a combination of ACTRESS and vessel-selective labeling to halve the scan time of vessel-selective 4D-MRA...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506939/the-choice-of-embedding-media-affects-image-quality-tissue-r-2-and-susceptibility-behaviors-in-post-mortem-brain-mr-microscopy-at-7-0t
#6
Petr Dusek, Vince Istvan Madai, Till Huelnhagen, Erik Bahn, Radoslav Matej, Jan Sobesky, Thoralf Niendorf, Julio Acosta-Cabronero, Jens Wuerfel
PURPOSE: The quality and precision of post-mortem MRI microscopy may vary depending on the embedding medium used. To investigate this, our study evaluated the impact of 5 widely used media on: (1) image quality, (2) contrast of high spatial resolution gradient-echo (T1 and T2 * -weighted) MR images, (3) effective transverse relaxation rate (R2 * ), and (4) quantitative susceptibility measurements (QSM) of post-mortem brain specimens. METHODS: Five formaldehyde-fixed brain slices were scanned using 7...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506877/real-time-simultaneous-shim-and-motion-measurement-and-correction-in-glycocest-mri-using-double-volumetric-navigators-dvnavs
#7
Gizeaddis L Simegn, Andre J W Van der Kouwe, Frances C Robertson, Ernesta M Meintjes, Ali Alhamud
PURPOSE: CEST MRI allows for indirect detection of molecules with exchangeable protons, measured as a reduction in water signal because of continuous transfer of saturated protons. CEST requires saturation pulses on the order of a second, as well as repeated acquisitions at different offset frequencies. The resulting extended scan time makes CEST susceptible to subject motion, which introduces field inhomogeneity, shifting offset frequencies and causing distortions in CEST spectra that resemble true CEST effects...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506796/flow-mr-fingerprinting
#8
Sebastian Flassbeck, Simon Schmidt, Peter Bachert, Mark E Ladd, Sebastian Schmitter
PURPOSE: To investigate the feasibility to quantify blood velocities within the magnetic resonance fingerprinting framework, while providing relaxometric maps of static tissue. METHODS: Bipolar gradients are inserted into an SSFP-based MRF sequence to achieve velocity-dependent signal phases, allowing tri-directional time-resolved velocity component quantification. The accuracy of both relaxometric mapping and velocity quantification was validated in vivo and in phantom studies...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506725/double-row-18-loop-transceive-32-loop-receive-tight-fit-array-provides-for-whole-brain-coverage-high-transmit-performance-and-snr-improvement-near-the-brain-center-at-9-4t
#9
Nikolai I Avdievich, Ioannis-Angelos Giapitzakis, Jonas Bause, Gunamony Shajan, Klaus Scheffler, Anke Henning
PURPOSE: To improve the transmit (Tx) and receive (Rx) performance of a human head array and provide whole-brain coverage at 9.4T, a novel 32-element array design was developed, constructed, and tested. METHODS: The array consists of 18 transceiver (TxRx) surface loops and 14 Rx-only vertical loops all placed in a single layer. The new design combines benefits of both TxRx and transmit-only-receive-only (ToRo) designs. The general idea of the design is that the total number of array elements (both TxRx and Rx) should not exceed the number of required Rx elements...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30506721/simple-and-broadly-applicable-automatic-quality-control-for-3d-1-h-mr-spectroscopic-imaging-data-of-the-prostate
#10
Nassim Tayari, Jiri Obels, Thiele Kobus, Tom W J Scheenen, Arend Heerschap
PURPOSE: Quality control (QC) is a prerequisite for clinical MR spectroscopic imaging (MRSI) to avoid that bad spectra hamper data interpretation. The aim of this work was to present a simple automatic QC for prostate 1 H MRSI that can handle data obtained with different commonly used pulse sequences, echo times, field strengths, and MR platforms. METHODS: A QC method was developed with a ratio (Qratio) where the numerator and the denominator are functions of several signal heights, logically combined for their positive or negative contribution to spectral quality...
December 2, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30488986/the-bold-sensitivity-of-rapid-steady-state-sequences
#11
Klaus Scheffler, Rahel Heule, Mario G Báez-Yánez, Bernd Kardatzki, Gabriele Lohmann
PURPOSE: Relaxation and dephasing of water protons embedded in a vascular network is driven by local magnetic field inhomogeneities around deoxygenated blood vessels. These effects strongly depend on the relation between mean diffusion length and diameter of blood vessels, as well as on the chosen imaging sequence. In this work, the BOLD sensitivity of steady-state sequences as a function of vessel size, field strength, and sequence parameters are analyzed. METHODS: Steady-state magnetization within a network of artificial cylinders is simulated with Monte Carlo methods for different coherence pathways...
November 29, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30488979/multishot-diffusion-prepared-magnitude-stabilized-balanced-steady-state-free-precession-sequence-for-distortion-free-diffusion-imaging
#12
Yu Gao, Fei Han, Ziwu Zhou, Xiaodong Zhong, Xiaoming Bi, John Neylon, Anand Santhanam, Yingli Yang, Peng Hu
PURPOSE: To develop and evaluate a multishot diffusion-prepared (DP) magnitude-stabilized balanced steady-state free precession (bSSFP) diffusion imaging sequence with improved geometric fidelity. METHODS: A signal spoiler (magnitude stabilizer; MS) was implemented in a DP-bSSFP diffusion sequence. Effects of magnitude stabilizers with respect to phase errors were simulated using Bloch simulation. Phantom study was conducted to compare the apparent diffusion coefficient (ADC) accuracy and geometric reliability, quantified using target registration error (TRE), with diffusion-weighted single-shot echo-planar imaging (DW-ssEPI)...
November 28, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30485536/assessment-of-cardiac-driven-liver-movements-with-filtered-harmonic-phase-image-representation-optical-flow-quantification-and-motion-amplification
#13
Stephan Hahn, Julie Absil, Olivier Debeir, Thierry Metens
PURPOSE: To characterize cardiac-driven liver movements using a harmonic phase image representation (HARP) with an optical flow quantification and motion amplification method. The method was applied to define the cardiac trigger delay providing minimal signal losses in liver DWI images. METHODS: The 16-s breath-hold balanced-SSFP time resolved 20 images/s were acquired at 3T in coronal and sagittal orientations. A peripheral pulse unit signal was recorded. Cardiac-triggered DWI images were acquired after different peripheral pulse unit delays...
November 28, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30478857/integrated-motion-correction-and-dictionary-learning-for-free-breathing-myocardial-t-1-mapping
#14
Yanjie Zhu, Jinkyu Kang, Chong Duan, Maryam Nezafat, Ulf Neisius, Jihye Jang, Reza Nezafat
PURPOSE: To develop and evaluate an integrated motion correction and dictionary learning (MoDic) technique to accelerate data acquisition for myocardial T1 mapping with improved accuracy. METHODS: MoDic integrates motion correction with dictionary learning-based reconstruction. A random undersampling scheme was implemented for slice-interleaved T1 mapping sequence to allow prospective undersampled data acquisition. Phantom experiments were performed to evaluate the effect of reconstruction on T1 measurement...
November 27, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30474312/influence-of-background-suppression-and-retrospective-realignment-on-free-breathing-renal-perfusion-measurement-using-pseudo-continuous-asl
#15
Manuel Taso, Arnaud Guidon, David C Alsop
PURPOSE: To assess the influence of background suppression and retrospective realignment on physiological noise and image quality in free-breathing renal pseudo-continuous arterial spin labeling (pCASL). METHODS: Ten subjects were scanned at 3T with a pCASL prepared single-slice coronal acquisition through the kidneys under free breathing. Multiple acquisitions were performed with various levels of residual background signal based on optimization of pulse timings to achieve specific background suppression levels (<2%, <5%, <10%, <20%)...
November 25, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30474159/magnetocaloric-materials-as-switchable-high-contrast-ratio-mri-labels
#16
Mladen Barbic, Stephen J Dodd, H Douglas Morris, Neil Dilley, Barbara Marcheschi, Alan Huston, Tim D Harris, Alan P Koretsky
PURPOSE: To develop switchable and tunable labels with high contrast ratio for MRI using magnetocaloric materials that have sharp first-order magnetic phase transitions at physiological temperatures and typical MRI magnetic field strengths. METHODS: A prototypical magnetocaloric material iron-rhodium (FeRh) was prepared by melt mixing, high-temperature annealing, and ice-water quenching. Temperature- and magnetic field-dependent magnetization measurements of wire-cut FeRh samples were performed on a vibrating sample magnetometer...
November 25, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30474151/3d-self-gated-cardiac-cine-imaging-at-3-tesla-using-stack-of-stars-bssfp-with-tiny-golden-angles-and-compressed-sensing
#17
Xiaoyong Zhang, Guoxi Xie, Na Lu, Yanchun Zhu, Zijun Wei, Shi Su, Caiyun Shi, Fei Yan, Xin Liu, Bensheng Qiu, Zhaoyang Fan
PURPOSE: To develop and evaluate an accelerated 3D self-gated cardiac cine imaging technique at 3 Tesla without the use of external electrocardiogram triggering or respiratory gating. METHODS: A 3D stack-of-stars balanced steady-state free precession sequence with a tiny golden angle sampling scheme was developed to reduced eddy current effect-related artefacts at 3 Tesla. Respiratory and cardiac motion were derived from a central 5-point self-gating signal extraction approach...
November 25, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30450755/reducing-the-number-of-samples-in-spatiotemporal-dmri-acquisition-design
#18
Patryk Filipiak, Rutger Fick, Alexandra Petiet, Mathieu Santin, Anne-Charlotte Philippe, Stephane Lehericy, Philippe Ciuciu, Rachid Deriche, Demian Wassermann
PURPOSE: Acquisition time is a major limitation in recovering brain white matter microstructure with diffusion magnetic resonance imaging. The aim of this paper is to bridge the gap between growing demands on spatiotemporal resolution of diffusion signal and the real-world time limitations. The authors introduce an acquisition scheme that reduces the number of samples under adjustable quality loss. METHODS: Finding a sampling scheme that maximizes signal quality and satisfies given time constraints is NP-hard...
November 19, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30450749/free-breathing-non-ecg-continuous-myocardial-t-1-mapping-with-cardiovascular-magnetic-resonance-multitasking
#19
Jaime L Shaw, Qi Yang, Zhengwei Zhou, Zixin Deng, Christopher Nguyen, Debiao Li, Anthony G Christodoulou
PURPOSE: To evaluate the accuracy and repeatability of a free-breathing, non-electrocardiogram (ECG), continuous myocardial T1 and extracellular volume (ECV) mapping technique adapted from the Multitasking framework. METHODS: The Multitasking framework is adapted to quantify both myocardial native T1 and ECV with a free-breathing, non-ECG, continuous acquisition T1 mapping method. We acquire interleaved high-spatial resolution image data and high-temporal resolution auxiliary data following inversion-recovery pulses at set intervals and perform low-rank tensor imaging to reconstruct images at 344 inversion times, 20 cardiac phases, and 6 respiratory phases...
November 19, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/30450638/evaluation-of-magnetohydrodynamic-effects-in-magnetic-resonance-electrical-impedance-tomography-at-ultra-high-magnetic-fields
#20
Atul S Minhas, Munish Chauhan, Fanrui Fu, Rosalind Sadleir
PURPOSE: Artifacts observed in experimental magnetic resonance electrical impedance tomography images were hypothesized to be because of magnetohydrodynamic (MHD) effects. THEORY AND METHODS: Simulations of MREIT acquisition in the presence of MHD and electrical current flow were performed to confirm findings. Laminar flow and (electrostatic) electrical conduction equations were bidirectionally coupled via Lorentz force equations, and finite element simulations were performed to predict flow velocity as a function of time...
November 19, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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