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https://www.readbyqxmd.com/read/28722201/susceptibility-induced-distortion-correction-in-hyperpolarized-echo-planar-imaging
#1
Jack J Miller, Angus Z Lau, Damian J Tyler
PURPOSE: Echo planar imaging is an attractive rapid imaging readout that can image hyperpolarized compounds in vivo. By alternating the sign of the phase encoding gradient waveform, spatial offsets arising from uncertain frequency shifts can be determined. We show here that blip-reversed echo planar imaging can also be used to correct for susceptibility and B0 inhomogeneity effects that would otherwise produce image-domain distortion in the heart. METHODS: Previously acquired blip-reversed cardiac 3D-Spectral-Spatial echo planar imaging volumetric timecourses of hyperpolarized [1-(13) C]pyruvate were distortion corrected by a deformation field estimated by reconstructing signal-to-noise ratio (SNR)-weighted progressively subsampled temporally summed images of each metabolite...
July 19, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28715700/a-simultaneous-multi-slice-selective-j-resolved-experiment-for-fully-resolved-scalar-coupling-information
#2
Qing Zeng, Liangjie Lin, Jinyong Chen, Yanqin Lin, Peter B Barker, Zhong Chen
Proton-proton scalar coupling plays an important role in molecular structure elucidation. Many methods have been proposed for revealing scalar coupling networks involving chosen protons. However, determining all JHH values within a fully coupled network remains as a tedious process. Here, we propose a method termed as simultaneous multi-slice selective J-resolved spectroscopy (SMS-SEJRES) for simultaneously measuring JHH values out of all coupling networks in a sample within one experiment. In this work, gradient-encoded selective refocusing, PSYCHE decoupling and echo planar spectroscopic imaging (EPSI) detection module are adopted, resulting in different selective J-edited spectra extracted from different spatial positions...
July 10, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28709153/age-reduces-microvascular-function-in-the-leg-independent-of-physical-activity
#3
Anne Tonson, Kayle E Noble, Ronald A Meyer, Mitchell R Rozman, Kevin T Foley, Jill M Slade
The microvasculature is critical in the control of blood flow. Aging and reduced physical activity (PA) may both decrease microvascular function. PURPOSE: The primary aim was to evaluate the influence of age on microvascular function in adults with similar PA levels. Secondary aims were to assess the reliability of muscle functional magnetic resonance imaging in older adults (OA) and the relationship between PA and microvascular function in OA. METHODS: Microvascular blood-oxygen-level dependent (BOLD) responses were measured in young adults (YA, n = 12, mean ± SD age = 21 ± 1 yr old, PA = 239 ± 73 × 10 counts per day) and OA (n = 13, 64 ± 4 yr old, PA = 203 ± 48 × 10 counts per day)...
August 2017: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/28706244/predicting-magnetostimulation-thresholds-in-the-peripheral-nervous-system-using-realistic-body-models
#4
Mathias Davids, Bastien Guérin, Matthias Malzacher, Lothar R Schad, Lawrence L Wald
Rapid switching of applied magnetic fields in the kilohertz frequency range in the human body induces electric fields powerful enough to cause Peripheral Nerve Stimulation (PNS). PNS has become one of the main constraints on the use of high gradient fields for fast imaging with the latest MRI gradient technology. In recent MRI gradients, the applied fields are powerful enough that PNS limits their application in fast imaging sequences like echo-planar imaging. Application of Magnetic Particle Imaging (MPI) to humans is similarly PNS constrained...
July 13, 2017: Scientific Reports
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
#5
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/28692129/distortion-free-diffusion-mri-using-an-mri-guided-tri-cobalt-60-radiotherapy-system-sequence-verification-and-preliminary-clinical-experience
#6
Yu Gao, Fei Han, Ziwu Zhou, Minsong Cao, Tania Kaprealian, Mitchell Kamrava, Chenyang Wang, John Neylon, Daniel A Low, Yingli Yang, Peng Hu
PURPOSE: Monitoring tumor response during the course of treatment and adaptively modifying treatment plan based on tumor biological feedback may represent a new paradigm for radiotherapy. Diffusion MRI has shown great promises in assessing and predicting tumor response to radiotherapy. However, the conventional diffusion-weighted single-shot echo-planar-imaging (DW-ssEPI) technique suffers from limited resolution, severe distortion and possibly inaccurate ADC at low field strength. The purpose of this work is to develop a reliable, accurate and distortion-free diffusion MRI technique that is practicable for longitudinal tumor response evaluation and adaptive radiotherapy on a 0...
July 10, 2017: Medical Physics
https://www.readbyqxmd.com/read/28686788/influence-of-physiological-noise-on-accelerated-2d-and-3d-resting-state-functional-mri-data-at-7%C3%A2-t
#7
Olivier Reynaud, João Jorge, Rolf Gruetter, José P Marques, Wietske van der Zwaag
PURPOSE: Physiological noise often dominates the blood-oxygen level-dependent (BOLD) signal fluctuations in high-field functional MRI (fMRI) data. Therefore, to optimize fMRI protocols, it becomes crucial to investigate how physiological signal fluctuations impact various acquisition and reconstruction schemes at different acquisition speeds. In particular, further differences can arise between 2D and 3D fMRI acquisitions due to different encoding strategies, thereby impacting fMRI sensitivity in potentially significant ways...
July 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28686785/liquid-crystal-phantom-for-validation-of-microscopic-diffusion-anisotropy-measurements-on-clinical-mri-systems
#8
Markus Nilsson, Johan Larsson, Dan Lundberg, Filip Szczepankiewicz, Thomas Witzel, Carl-Fredrik Westin, Karin Bryskhe, Daniel Topgaard
PURPOSE: To develop a phantom for validating MRI pulse sequences and data processing methods to quantify microscopic diffusion anisotropy in the human brain. METHODS: Using a liquid crystal consisting of water, detergent, and hydrocarbon, we designed a 0.5-L spherical phantom showing the theoretically highest possible degree of microscopic anisotropy. Data were acquired on the Connectome scanner using echo-planar imaging signal readout and diffusion encoding with axisymmetric b-tensors of varying magnitude, anisotropy, and orientation...
July 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28678737/functional-brain-mri-in-patients-complaining-of-electrohypersensitivity-after-long-term-exposure-to-electromagnetic-fields
#9
Gunnar Heuser, Sylvia A Heuser
INTRODUCTION: Ten adult patients with electromagnetic hypersensitivity underwent functional magnetic resonance imaging (fMRI) brain scans. All scans were abnormal with abnormalities which were consistent and similar. It is proposed that fMRI brain scans be used as a diagnostic aid for determining whether or not a patient has electromagnetic hypersensitivity. Over the years we have seen an increasing number of patients who had developed multi system complaints after long term repeated exposure to electromagnetic fields (EMFs)...
July 5, 2017: Reviews on Environmental Health
https://www.readbyqxmd.com/read/28673676/detection-of-cholesteatoma-high-resolution-dwi-using-rs-epi-and-parallel-imaging-at-3-tesla
#10
O Algin, H Aydın, E Ozmen, G Ocakoglu, S Bercin, D A Porter, A Kutluhan
The purpose of this study is to evaluate the impact of RS-EPI-DWI in the detection of cholesteatoma and to compare with single-shot echo-planar DWI (SS-EPI-DWI). Diffusion-weighted and apparent diffusion-coefficient (ADC) images were obtained using RS-EPI and SS-EPI techniques in 30 patients. Presence of cholesteatoma (3 point scale), amount of artefacts (4 point scale), visibility (4 point scale), and ADC values of the lesions were assessed. The results of both techniques were compared with each other and gold-standard (GS) test results...
June 30, 2017: Journal of Neuroradiology. Journal de Neuroradiologie
https://www.readbyqxmd.com/read/28666879/correction-of-metal-induced-susceptibility-artifacts-for-functional-mri-during-deep-brain-stimulation
#11
Myung-Ho In, Shinho Cho, Yunhong Shu, Hoon-Ki Min, Matt A Bernstein, Oliver Speck, Kendall H Lee, Hang Joon Jo
Functional magnetic resonance imaging (fMRI) is an emerging tool for investigating brain activation associated with, or modulated by, deep brain stimulation (DBS). However, DBS-fMRI generally suffers from severe susceptibility to artifacts in regions near the metallic stimulation electrodes, as well as near tissue/air boundaries of the brain. These result in strong intensity and geometric distortions along the phase-encoding (PE) (i.e., blipped) direction in gradient-echo echo-planar imaging (GE-EPI). Distortion presents a major challenge to conducting reliable data analysis and in interpreting the findings...
June 27, 2017: NeuroImage
https://www.readbyqxmd.com/read/28666091/a-combined-use-of-intravoxel-incoherent-motion-mri-parameters-can-differentiate-early-stage-hepatitis-b-fibrotic-livers-from-healthy-livers
#12
Yì Xiáng J Wáng, Min Deng, Yáo T Li, Hua Huang, Jason Chi Shun Leung, Weitian Chen, Pu-Xuan Lu
This study investigated a combined use of intravoxel incoherent motion (IVIM) parameters, Dslow ( D), PF ( f), and Dfast ( D*), for liver fibrosis evaluation. Sixteen healthy volunteers (F0) and 33 hepatitis-b patients (stage F1 = 15, stage F2-4 = 18) were included. With a 1.5 T MR scanner and respiration gating, IVIM diffusion-weighted imaging was acquired using a single-shot echo-planar imaging sequence with 10 b values of 10, 20, 40, 60, 80, 100, 150, 200, 400, and 800 s/mm(2). Signal measurement was performed on right liver parenchyma...
June 1, 2017: SLAS Technology
https://www.readbyqxmd.com/read/28656631/effect-of-myelin-water-exchange-on-dti-derived-parameters-in-diffusion-mri-elucidation-of-te-dependence
#13
Mu Lin, Hongjian He, Qiqi Tong, Qiuping Ding, Xu Yan, Thorsten Feiweier, Jianhui Zhong
PURPOSE: Water exchange exists between different neuronal compartments of brain tissue but is often ignored in most diffusion models. The goal of the current study was to demonstrate the dependence of diffusion measurements on echo time (TE) in the human brain and to investigate the underlying effects of myelin water exchange. METHODS: Five healthy subjects were examined with single-shot pulsed-gradient spin-echo echo-planar imaging with fixed duration (δ) and separation (Δ) of diffusion gradient pulses and a set of varying TEs...
June 27, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28653477/radiomic-analysis-of-soft-tissues-sarcomas-can-distinguish-intermediate-from-high-grade-lesions
#14
Valentina D A Corino, Eros Montin, Antonella Messina, Paolo G Casali, Alessandro Gronchi, Alfonso Marchianò, Luca T Mainardi
PURPOSE: To assess the feasibility of grading soft tissue sarcomas (STSs) using MRI features (radiomics). MATERIALS AND METHODS: MRI (echo planar SE, 1.5T) from 19 patients with STSs and a known histological grading, were retrospectively analyzed. The apparent diffusion coefficient (ADC) maps, obtained by diffusion-weighted imaging acquisitions, were analyzed through 65 radiomic features, intensity-based (first order statistics, FOS) and texture (gray level co-occurrence matrix, GLCM; and gray level run length matrix, GLRLM) features...
June 27, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28653470/characterization-of-pseudo-continuous-arterial-spin-labeling-simulations-and-experimental-validation
#15
Kathrin Lorenz, Toralf Mildner, Torsten Schlumm, Harald E Möller
PURPOSE: To characterize pseudo-continuous arterial spin labeling (pCASL) through simulations of spin inversion and to discuss suitable parameter settings for measuring cerebral perfusion. METHODS: Simulations of arterial spin inversion in pCASL were performed based on the Bloch equation. Both the labeling and the control condition of pCASL were analyzed separately, and the labeling efficiency, α, was calculated depending on the averages of both, the radiofrequency (RF) field amplitude and labeling gradient strength...
June 26, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28653363/quiet-echo-planar-imaging-for-functional-and-diffusion-mri
#16
Jana Hutter, Anthony N Price, Lucilio Cordero-Grande, Shaihan Malik, Giulio Ferrazzi, Andreia Gaspar, Emer J Hughes, Daan Christiaens, Laura McCabe, Torben Schneider, Mary A Rutherford, Joseph V Hajnal
PURPOSE: To develop a purpose-built quiet echo planar imaging capability for fetal functional and diffusion scans, for which acoustic considerations often compromise efficiency and resolution as well as angular/temporal coverage. METHODS: The gradient waveforms in multiband-accelerated single-shot echo planar imaging sequences have been redesigned to minimize spectral content. This includes a sinusoidal read-out with a single fundamental frequency, a constant phase encoding gradient, overlapping smoothed CAIPIRINHA blips, and a novel strategy to merge the crushers in diffusion MRI...
June 26, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28652524/single-breath-hold-whole-heart-unenhanced-coronary-mra-using-multi-shot-gradient-echo-epi-at-3t-comparison-with-free-breathing-turbo-field-echo-coronary-mra-on-healthy-volunteers
#17
Yuji Iyama, Takeshi Nakaura, Yasunori Nagayama, Seitaro Oda, Daisuke Utsunomiya, Masafumi Kidoh, Hideaki Yuki, Kenichiro Hirata, Tomohiro Namimoto, Mika Kitajima, Kosuke Morita, Yoshinori Funama, Atsushi Takemura, Tomoyuki Okuaki, Yasuyuki Yamashita
PURPOSE: We investigated the feasibility of single breath hold unenhanced coronary magnetic resonance angiography (MRA) using multi-shot gradient echo planar imaging (MSG-EPI) on a 3T-scanner. METHODS: Fourteen volunteers underwent single breath hold coronary MRA with a MSG-EPI and free-breathing turbo field echo (TFE) coronary MRA at 3T. The acquisition time, signal to noise ratio (SNR), and the contrast of the sequences were compared with the paired t-test. Readers evaluated the image contrast, noise, sharpness, artifacts, and the overall image quality...
June 26, 2017: Magnetic Resonance in Medical Sciences: MRMS
https://www.readbyqxmd.com/read/28639370/b0-concomitant-field-compensation-for-mri-systems-employing-asymmetric-transverse-gradient-coils
#18
Paul T Weavers, Shengzhen Tao, Joshua D Trzasko, Louis M Frigo, Yunhong Shu, Matthew A Frick, Seung-Kyun Lee, Thomas K-F Foo, Matt A Bernstein
PURPOSE: Imaging gradients result in the generation of concomitant fields, or Maxwell fields, which are of increasing importance at higher gradient amplitudes. These time-varying fields cause additional phase accumulation, which must be compensated for to avoid image artifacts. In the case of gradient systems employing symmetric design, the concomitant fields are well described with second-order spatial variation. Gradient systems employing asymmetric design additionally generate concomitant fields with global (zeroth-order or B0 ) and linear (first-order) spatial dependence...
June 21, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28639310/high-resolution-31-p-echo-planar-spectroscopic-imaging-in-vivo-at-7t
#19
Andreas Korzowski, Peter Bachert
PURPOSE: Conventional (31) P chemical shift imaging is time-consuming and yields only limited spatial resolution. The purpose of this study was to demonstrate feasibility of (31) P echo-planar spectroscopic imaging (EPSI) in vivo at 7T. METHODS: A 3D (31) P EPSI sequence with trapezoidal-shaped gradient pulses was implemented on a 7T MR scanner. To increase spectral width with reduced demand on gradient performance, a multishot approach was chosen. Acquisition weighting and (31) P-{(1) H} double resonance for nuclear Overhauser signal enhancement were applied to increase sensitivity...
June 21, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28637508/hyperpolarized-13-c-urea-myocardial-first-pass-perfusion-imaging-using-velocity-selective-excitation
#20
Maximilian Fuetterer, Julia Busch, Sophie M Peereboom, Constantin von Deuster, Lukas Wissmann, Miriam Lipiski, Thea Fleischmann, Nikola Cesarovic, Christian T Stoeck, Sebastian Kozerke
BACKGROUND: A velocity-selective binomial excitation scheme for myocardial first-pass perfusion measurements with hyperpolarized (13)C substrates, which preserves bolus magnetization inside the blood pool, is presented. The proposed method is evaluated against gadolinium-enhanced (1)H measurements in-vivo. METHODS: The proposed excitation with an echo-planar imaging readout was implemented on a clinical CMR system. Dynamic myocardial stress perfusion images were acquired in six healthy pigs after bolus injection of hyperpolarized (13)C urea with the velocity-selective vs...
June 21, 2017: Journal of Cardiovascular Magnetic Resonance
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