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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/27917529/accuracy-precision-and-reproducibility-of-myocardial-t1-mapping-a-comparison-of-four-t1-estimation-algorithms-for-modified-look-locker-inversion-recovery-molli
#1
Jiaxin Shao, Dapeng Liu, Kyunghyun Sung, Kim-Lien Nguyen, Peng Hu
PURPOSE: To compare the accuracy and precision of four different T1 estimation algorithms for modified Look-Locker inversion recovery (MOLLI). METHODS: Four T1 estimation algorithms, including the original fit, inversion group (IG) fit, instantaneous signal loss simulation (InSiL), and Bloch equation simulation with slice profile correction (BLESSPC) were studied. T1 estimation accuracy, precision, reproducibility, and sensitivity to heart rate (HR), flip angle (FA), and acquisition scheme (AcS) variations were compared in simulation, phantom, and volunteer studies...
December 4, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27917528/the-ultimate-signal-to-noise-ratio-in-realistic-body-models
#2
Bastien Guérin, Jorge F Villena, Athanasios G Polimeridis, Elfar Adalsteinsson, Luca Daniel, Jacob K White, Lawrence L Wald
PURPOSE: We compute the ultimate signal-to-noise ratio (uSNR) and G-factor (uGF) in a realistic head model from 0.5 to 21 Tesla. METHODS: We excite the head model and a uniform sphere with a large number of electric and magnetic dipoles placed at 3 cm from the object. The resulting electromagnetic fields are computed using an ultrafast volume integral solver, which are used as basis functions for the uSNR and uGF computations. RESULTS: Our generalized uSNR calculation shows good convergence in the sphere and the head and is in close agreement with the dyadic Green's function approach in the uniform sphere...
December 4, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27917527/simultaneous-orthogonal-plane-imaging
#3
Nikolai J Mickevicius, Eric S Paulson
PURPOSE: Intrafraction motion can result in a smearing of planned external beam radiation therapy dose distributions, resulting in an uncertainty in dose actually deposited in tissue. The purpose of this paper is to present a pulse sequence that is capable of imaging a moving target at a high frame rate in two orthogonal planes simultaneously for MR-guided radiotherapy. THEORY: By balancing the zero gradient moment on all axes, slices in two orthogonal planes may be spatially encoded simultaneously...
December 4, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27917520/sensitive-enhancement-of-vessel-wall-imaging-with-an-endoesophageal-wireless-amplified-nmr-detector-wand
#4
Xianchun Zeng, Mladen Barbic, Liangliang Chen, Chunqi Qian
PURPOSE: To improve the imaging quality of vessel walls with an endoesophageal Wireless Amplified NMR Detector (WAND). METHODS: A cylindrically shaped double-frequency resonator has been constructed with a single metal wire that is self-connected by a pair of nonlinear capacitors. The double-frequency resonator can convert wirelessly provided pumping power into amplified MR signals. This compact design makes the detector easily insertable into a rodent esophagus...
December 4, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27910126/gradient-echo-epi-using-a-high-degree-shim-insert-coil-at-7%C3%A2-t-implications-for-bold-fmri
#5
Tae Kim, Yoojin Lee, Tiejun Zhao, Hoby P Hetherington, Jullie W Pan
PURPOSE: To quantitatively assess the effects of high degree and order (1(st) -4(th+) ) relative to 1(st) -2(nd) degree B0 shimming at 7 Tesla (T) on gradient-echo echo planar imaging (GE-EPI) and blood-oxygen-level dependent (BOLD) activation. METHODS: Simulations and GE-EPI were performed at (2mm)(3) and (3mm)(3) resolution, evaluating the temporal signal-to-noise ratio (tSNR), transverse relaxivity ( R2*), BOLD % signal change and activated pixel counts in a breath-hold task...
December 1, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27905145/the-public-multi-coil-information-pumcin-policy
#6
Christoph Juchem, Robin A de Graaf
PURPOSE: Multi-coil (MC) magnetic field modeling has emerged as a viable alternative to conventional field generation based on spherical harmonic shapes, and an active MC community is forming. Although all MC applications share the same modeling concept, the specific MC designs can largely differ as a result of disparities in region of interest (eg, human versus rodent), intended MR application (eg, B0 shimming versus spatial encoding), or other experimental constraints (eg, available bore space or integration with radiofrequency technology)...
December 1, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27900794/fast-and-efficient-free-induction-decay-mr-spectroscopic-imaging-of-the-human-brain-at-9-4-tesla
#7
Grzegorz L Chadzynski, Jonas Bause, Gunamony Shajan, Rolf Pohmann, Klaus Scheffler, Philipp Ehses
PURPOSE: The purpose of this work was to develop a fast and efficient MRSI-FID acquisition scheme and test its performance in vivo. The aim was to find a trade-off between the minimal total acquisition time and signal-to-noise ratio of the acquired spectra. METHODS: Measurements were performed on a 9.4 Tesla system. Sequence optimization included redesign of water suppression, optimization of the sequence gradients, and improvement of the sampling efficiency by minimizing the read-out time...
November 29, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27888545/anti-angiogenic-therapy-affects-the-relationship-between-tumor-vascular-structure-and-function-a-correlation-study-between-micro-computed-tomography-angiography-and-dynamic-contrast-enhanced-mri
#8
Eugene Kim, Jana Kim, Gunhild Mari Maelandsmo, Berit Johansen, Siver Andreas Moestue
PURPOSE: To compare the effects of two anti-angiogenic drugs, bevacizumab and a cytosolic phospholipase A2-α inhibitor (AVX235), on the relationship between vascular structure and dynamic contrast enhanced (DCE)-MRI measurements in a patient-derived breast cancer xenograft model. METHODS: Mice bearing MAS98.12 tumors were randomized into three groups: bevacizumab-treated (n = 9), AVX235-treated (n = 9), and control (n = 8). DCE-MRI was performed pre- and post-treatment...
November 25, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27888543/segmented-simultaneous-multi-slice-diffusion-weighted-imaging-with-generalized-trajectories
#9
Michael Herbst, Weiran Deng, Thomas Ernst, V Andrew Stenger
PURPOSE: The purpose of this work is to develop and evaluate a single framework for the use of Cartesian and non-Cartesian segmented trajectories for rapid and robust simultaneous multislice (SMS) diffusion weighted imaging (DWI) at 3 Telsa (T). METHODS: A generalized SMS approach with intrinsic phase navigation using Multiplexed Sensitivity Encoding (MUSE) was developed. Segmented blipped-controlled aliasing in parallel imaging echo planar imaging (EPI) and z-gradient modulated spiral trajectories were examined using SMS DWI scans at 3T with a 32-channel head coil...
November 25, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27888530/perturbation-of-longitudinal-relaxation-rate-in-rotating-frame-plrf-analysis-for-quantification-of-chemical-exchange-saturation-transfer-signal-in-a-transient-state
#10
Yi Wang, Yaoyu Zhang, Xuna Zhao, Bing Wu, Jia-Hong Gao
PURPOSE: To develop a novel analytical method for quantification of chemical exchange saturation transfer (CEST) in the transient state. The proposed method aims to reduce the effects of non-chemical-exchange (non-CE) parameters on the CEST signal, emphasizing the effect of chemical exchange. METHODS: The difference in the longitudinal relaxation rate in the rotating frame ( ΔR1ρ) was calculated based on perturbation of the Z-value by R1ρ, and a saturation-pulse-amplitude-compensated exchange-dependent relaxation rate (SPACER) was determined with a high-exchange-rate approximation...
November 25, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27885707/spatial-resolution-and-velocity-field-improvement-of-4d-flow-mri
#11
Fraser M Callaghan, Stuart M Grieve
PURPOSE: 4D-flow MRI obtains a time-dependent 3D velocity field; however, its use for the calculation of higher-order parameters is limited by noise. We present an algorithm for denoising 4D-flow data. THEORY AND METHODS: By integrating a velocity field and eliminating streamlines in noisy flow, depicted by high curvature, a denoised dataset may be extracted. This method, defined as the velocity field improvement (VFIT) algorithm, was validated in an analytical dataset and using in vivo data in comparison with a computation fluid dynamics (CFD) simulation...
November 24, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27873353/adaptively-optimized-combination-aoc-of-phased-array-mr-spectroscopy-data-in-the-presence-of-correlated-noise-compared-with-noise-decorrelated-or-whitened-methods
#12
Minjie Wu, Liang Fang, Charles E Ray, Anand Kumar, Shaolin Yang
PURPOSE: A method for adaptively optimized combination (AOC) of MR spectroscopic data from a coil array was recently introduced. The superior performance of the AOC method is evident when compared with the methods that assume uncorrelated noise between coil elements. However, it is unclear whether the AOC method represents the most optimal combination in the presence of correlated noise, when compared with the noise-decorrelated or whitened methods that specifically tackle the correlated noise between coil elements...
November 21, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27868238/suppression-of-ghost-artifacts-arising-from-long-t1-species-in-segmented-inversion-recovery-imaging
#13
Elizabeth R Jenista, Wolfgang G Rehwald, Nayla H Chaptini, Han W Kim, Michele A Parker, David C Wendell, Enn-Ling Chen, Raymond J Kim
PURPOSE: We demonstrate an improved segmented inversion-recovery sequence that suppresses ghost artifacts arising from tissues with long T1 ( > 1.5 s). THEORY AND METHODS: Long T1 species such as pericardial fluid can create bright ghost artifacts in segmented, inversion-recovery MRI because of oscillations in longitudinal magnetization between segments. A single dummy acquisition at the beginning of the sequence can reduce oscillations; however, its effectiveness in suppressing long T1 artifacts is unknown...
November 20, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27868234/efficient-31-p-band-inversion-transfer-approach-for-measuring-creatine-kinase-activity-atp-synthesis-and-molecular-dynamics-in-the-human-brain-at-7-t
#14
Jimin Ren, A Dean Sherry, Craig R Malloy
PURPOSE: To develop an efficient (31) P magnetic resonance spectroscopy (MRS) method for measuring creatine kinase (CK) activity, adenosine triphosphate (ATP) synthesis, and motion dynamics in the human brain at 7 Tesla (T). METHODS: Three band inversion modules differing in center frequency were used to induce magnetization transfer (MT) effect in three exchange pathways: (i) CK-mediated reaction PCr → γ-ATP; (ii) de novo ATP synthesis Pi → γ-ATP; and (iii) ATP intramolecular (31) P-(31) P cross-relaxation γ-(α-) ↔ β-ATP...
November 20, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27859552/low-pass-imaging-of-dynamic-acquisitions-lida-with-a-group-oriented-registration-goreg-for-proton-mr-imaging-of-lung-ventilation
#15
Andreas Voskrebenzev, Marcel Gutberlet, Till F Kaireit, Frank Wacker, Jens Vogel-Claussen
PURPOSE: To compare low-pass imaging dynamic acquisitions (LIDA) approach in combination with a group-oriented registration (GOREG) scheme with conventional Fourier decomposition (FD). METHODS: Dynamic images of six healthy volunteers and one chronic obstructive pulmonary disease (COPD) patient were acquired on a 1.5 Tesla scanner using a spoiled gradient echo sequence. For the volunteers each slice was acquired during regular (RB) and irregular breathing (IB). For conventional registration (CR), all images were directly registered to the intermediate respiratory position...
November 18, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27859618/in-vivo-measurement-of-a-new-source-of-contrast-the-dipolar-relaxation-time-t1d-using-a-modified-inhomogeneous-magnetization-transfer-ihmt-sequence
#16
Gopal Varma, Olivier M Girard, Valentin H Prevost, Aaron K Grant, Guillaume Duhamel, David C Alsop
PURPOSE: This paper describes a technique that can be used in vivo to measure the dipolar relaxation time, T1D , of macromolecular protons contributing to magnetization transfer (MT) in tissues and to produce quantitative T1D maps. THEORY AND METHODS: The technique builds upon the inhomogeneous MT (ihMT) technique that is particularly sensitive to tissue components with long T1D . A standard ihMT experiment was altered to introduce a variable time for switching between positive and negative offset frequencies for RF saturation...
November 17, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27859614/a-comparison-of-navigators-snap-shot-field-monitoring-and-probe-based-field-model-training-for-correcting-b0-induced-artifacts-in-t2-weighted-images-at-7%C3%A2-t
#17
Joep Wezel, Vincent O Boer, Tijl A van der Velden, Andrew G Webb, Dennis W J Klomp, Maarten J Versluis, Matthias J P van Osch, Anders Garpebring
PURPOSE: To compare methods for estimating B0 maps used in retrospective correction of high-resolution anatomical images at ultra-high field strength. The B0 maps were obtained using three methods: (1) 1D navigators and coil sensitivities, (2) field probe (FP) data and a low-order spherical harmonics model, and (3) FP data and a training-based model. METHODS: Data from nine subjects were acquired while they performed activities inducing B0 field fluctuations. Estimated B0 fields were compared with reference data, and the reductions of artifacts were compared in corrected T2* images...
November 17, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27859575/monitoring-acute-metabolic-changes-in-the-liver-and-kidneys-induced-by-fructose-and-glucose-using-hyperpolarized-2-13-c-dihydroxyacetone
#18
Irene Marco-Rius, Cornelius von Morze, Renuka Sriram, Peng Cao, Gene-Yuan Chang, Eugene Milshteyn, Robert A Bok, Michael A Ohliger, David Pearce, John Kurhanewicz, Peder E Z Larson, Daniel B Vigneron, Matthew Merritt
PURPOSE: To investigate acute changes in glucose metabolism in liver and kidneys in vivo after a bolus injection of either fructose or glucose, using hyperpolarized [2-(13) C]dihydroxyacetone. METHODS: Spatially registered, dynamic, multislice MR spectroscopy was acquired for the metabolic products of [2-(13) C]dihydroxyacetone in liver and kidneys. Metabolism was probed in 13 fasted rats at three time points: 0, 70, and 140 min. At 60 min, rats were injected intravenously with fructose (n = 5) or glucose (n = 4) at 0...
November 17, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27859563/direct-estimation-of-tracer-kinetic-parameter-maps-from-highly-undersampled-brain-dynamic-contrast-enhanced-mri
#19
Yi Guo, Sajan Goud Lingala, Yinghua Zhu, R Marc Lebel, Krishna S Nayak
PURPOSE: The purpose of this work was to develop and evaluate a T1 -weighted dynamic contrast enhanced (DCE) MRI methodology where tracer-kinetic (TK) parameter maps are directly estimated from undersampled (k,t)-space data. THEORY AND METHODS: The proposed reconstruction involves solving a nonlinear least squares optimization problem that includes explicit use of a full forward model to convert parameter maps to (k,t)-space, utilizing the Patlak TK model. The proposed scheme is compared against an indirect method that creates intermediate images by parallel imaging and compressed sensing before to TK modeling...
November 17, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27859558/7-tesla-22-channel-wrap-around-coil-array-for-cervical-spinal-cord-and-brainstem-imaging
#20
Bei Zhang, Alan C Seifert, Joo-Won Kim, Joseph Borrello, Junqian Xu
PURPOSE: Increased signal-to-noise ratio and blood oxygenation level-dependent sensitivity at 7 Tesla (T) have the potential to enable high-resolution imaging of the human cervical spinal cord and brainstem. We propose a new two-panel radiofrequency coil design for these regions to fully exploit the advantages of ultra-high field. METHODS: A two-panel array, containing four transmit/receive and 18 receive-only elements fully encircling the head and neck, was constructed following simulations demonstrating the B1+ and specific absorption rate (SAR) benefits of two-panel over one-panel arrays...
November 17, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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