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Magnetic Resonance Imaging

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https://www.readbyqxmd.com/read/28526432/quantitative-susceptibility-mapping-using-principles-of-echo-shifting-with-a-train-of-observations-sequence-on-1-5t-mri
#1
Hirohito Kan, Nobuyuki Arai, Harumasa Kasai, Hiroshi Kunitomo, Yasujiro Hirose, Yuta Shibamoto
PURPOSE: To evaluate the accuracy of susceptibility estimated from the principles of echo shifting with a train of observations (PRESTO) sequence using a 1.5T MRI system, we conducted experiments on the human brain using the PRESTO sequence and compared our results with the susceptibility obtained from spoiled gradient-recalled echo (GRE) sequence with flow compensation using quantitative susceptibility mapping (QSM) reconstruction. MATERIALS AND METHODS: Experiments on the human brain were conducted on 12 healthy volunteers (27±4years) using PRESTO and spoiled GRE sequences on a 1...
May 16, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28526431/measurement-of-apt-using-a-combined-cert-arex-approach-with-varying-duty-cycles
#2
Zhongliang Zu, Hua Li, Junzhong Xu, Xiao-Yong Zhang, Moritz Zaiss, Ke Li, Mark D Does, John C Gore, Daniel F Gochberg
The goal is to develop an imaging method where contrast reflects amide-water magnetization exchange, with minimal signal contributions from other sources. Conventional chemical exchange saturation transfer (CEST) imaging of amides (often called amide proton transfer, or APT, and quantified by the metric MTRasym) is confounded by several factors unrelated to amides, such as aliphatic protons, water relaxation, and macromolecular magnetization transfer. In this work, we examined the effects of combining our previous chemical exchange rotation (CERT) approach with the non-linear AREX method while using different duty cycles (DC) for the label and reference scans...
May 16, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28526430/combination-of-integrated-dynamic-shimming-and-readout-segmented-echo-planar-imaging-for-diffusion-weighted-mri-of-the-head-and-neck-region-at-3tesla
#3
Sven S Walter, Wei Liu, Alto Stemmer, Petros Martirosian, Konstantin Nikolaou, Mike Notohamiprodjo, Sergios Gatidis
PURPOSE: To evaluate the performance of combined integrated slice-by-slice shimming and readout-segmented EPI (irsEPI) for diffusion-weighted MR imaging (DWI) of the neck at 3Tesla. METHODS: This study was approved by the local ethics committee. An anthropometric phantom of the head/neck region incorporating compartments with different diffusivities was constructed. In vivo measurements were performed in 10 healthy volunteers. DWI of the phantom and volunteers was performed on a 3Tesla MR scanner using single shot EPI (sEPI), a prototype single shot EPI with integrated slice-by-slice shimming (iEPI), readout segmented EPI (rsEPI) and a prototype readout segmented EPI with integrated shimming irsEPI...
May 16, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28522366/a-level-set-method-for-multiple-sclerosis-lesion-segmentation
#4
Yue Zhao, Shuxu Guo, Min Luo, Xue Shi, Michel Bilello, Shaoxiang Zhang, Chunming Li
In this paper, we present a level set method for multiple sclerosis (MS) lesion segmentation from FLAIR Images in the presence of intensity inhomogeneities. We use a three-phase level set formulation of segmentation and bias field estimation to segment MS lesions and normal tissue region (including GM and WM) and CSF and the background from FLAIR images. To save computational load, we derive a two-phase formulation from the original multi-phase level set formulation to segment the MS lesions and normal tissue regions...
May 15, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28479342/normalizing-data-from-gaba-edited-mega-press-implementations-at-3-tesla
#5
Ashley D Harris, Nicolaas A J Puts, S Andrea Wijtenburg, Laura M Rowland, Mark Mikkelsen, Peter B Barker, C John Evans, Richard A E Edden
Standardization of results is an important milestone in the maturation of any truly quantitative methodology. For instance, a lack of measurement agreement across imaging platforms limits multisite studies, between-study comparisons based on the literature, and inferences based on and the generalizability of results. In GABA-edited MEGA-PRESS, two key sources of differences between implementations are: differences in editing efficiency of GABA and the degree of co-editing of macromolecules (MM). In this work, GABA editing efficiency κ and MM-co-editing μ constants are determined for three widely used MEGA-PRESS implementations (on the most common MRI platforms; GE, Philips, and Siemens) by phantom experiments...
May 4, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28479341/towards-intrinsic-r2-imaging-in-the-prostate-at-3-and-7tesla
#6
Mariska P Luttje, Laurens D van Buuren, Peter R Luijten, Marco van Vulpen, Uulke A van der Heide, Dennis W J Klomp
PURPOSE: Hypoxia is an important marker for resistance to therapy. In this study, we quantify the macroscopic effects of R2* mapping in prostate cancer patients incorporating susceptibility matching and field strengths effects. MATERIALS AND METHODS: 91 patients were scanned without endorectal coil (ERC) at 3T. Only when rectal gas was absent, data was included for analysis. Another group of 10 patients was scanned using a susceptibility matched ERC. To assess the residual contamination of R2 and macroscopic field non-uniformities, a group of 10 patients underwent ultra-high resolution 7T MRI...
May 4, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28476308/magnetic-resonance-elastography-of-the-pancreas-measurement-reproducibility-and-relationship-with-age
#7
Arunark Kolipaka, Samuel Schroeder, Xiaokui Mo, Zarine Shah, Phil A Hart, Darwin L Conwell
PURPOSE: To determine magnetic resonance elastography (MRE)-derived stiffness of pancreas in healthy volunteers with emphasis on: 1) short term and midterm repeatability; and 2) variance as a function of age. METHODS: Pancreatic MRE was performed on 22 healthy volunteers (age range:20-64years) in a 3T-scanner. For evaluation of reproducibility of stiffness estimates, the scans were repeated per volunteer on the same day (short term) and one month apart (midterm)...
May 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28461132/a-non-contrast-cmr-index-for-assessing-myocardial-fibrosis
#8
Qian Yin, Dana Abendschein, David Muccigrosso, Robert O'Connor, Thomas Goldstein, Jie Zheng
PURPOSE: Safe, sensitive, and non-invasive imaging methods to assess the presence, extent, and turnover of myocardial fibrosis are needed for early stratification of risk in patients who might develop heart failure after myocardial infarction. We describe a non-contrast cardiac magnetic resonance (CMR) approach for sensitive detection of myocardial fibrosis using a canine model of myocardial infarction and reperfusion. METHODS: Seven dogs had coronary thrombotic occlusion of the left anterior descending coronary arteries followed by fibrinolytic reperfusion...
April 28, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28454765/black-blood-t2-mapping-with-delay-alternating-with-nutation-for-tailored-excitation
#9
Shi Su, Yanan Ren, Caiyun Shi, Xiaoyong Zhang, Jim X Ji, Yongqin Zhang, Xin Liu, Guoxi Xie
PURPOSE: To develop a black-blood T2* mapping method using a Delay Alternating with Nutation for Tailored Excitation (DANTE) preparation combined with a multi-echo gradient echo (GRE) readout (DANTE-GRE). MATERIALS AND METHODS: Simulations of the Bloch equation for DANTE-GRE were performed to optimize sequence parameters. After optimization, the sequence was applied to a phantom scan and to neck and lower extremity scans conducted on 12 volunteers at 3T using DANTE-GRE, Motion-Sensitized Driven Equilibrium (MSDE)-GRE, and multi-echo GRE...
April 25, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28438714/the-effect-of-morphological-and-microstructural-integrity-of-the-corpus-callosum-on-cognition-fatigue-and-depression-in-mildly-disabled-ms-patients
#10
Jeroen Van Schependom, Jeroen Gielen, Jorne Laton, Georgios Sotiropoulos, Anne-Marie Vanbinst, Johan De Mey, Dirk Smeets, Guy Nagels
AIM: To assess the value of callosal morphological and microstructural integrity in assessing different cognitive domains, fatigue and depression in mildly disabled multiple sclerosis (MS) patients. MATERIALS AND METHODS: We assessed 29 mildly disabled MS patients and 15 healthy controls using 3T magnetic resonance images (T1-weighted, FLAIR and DTI) and neuropsychological tests assessing different cognitive functions, depression and fatigue. We compared the added value of morphological measures (corpus callosum area corrected for total intracranial volume, index, circularity and the more detailed thickness profile) and diffusion features (fractional anisotropy and mean diffusivity) in multilinear models including standard clinical and whole-brain parameters in assessing neuropsychological scores...
April 24, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28438712/empirical-consideration-of-the-effects-of-acquisition-parameters-and-analysis-model-on-clinically-feasible-q-ball-imaging
#11
Kurt G Schilling, Vishwesh Nath, Justin A Blaber, Prasanna Parvathaneni, Adam W Anderson, Bennett A Landman
Q-ball imaging (QBI) is a popular high angular resolution diffusion imaging (HARDI) technique used to study brain architecture in vivo. Simulation and phantom-based studies suggest that QBI results are affected by the b-value, the number of diffusion weighting directions, and the signal-to-noise ratio (SNR). However, optimal acquisition schemes for QBI in clinical settings are largely undetermined given empirical (observed) imaging considerations. In this study, we acquire a HARDI dataset at five b-values with 11 repetitions on a single subject to investigate the effects of acquisition scheme and subsequent analysis models on the accuracy and precision of measures of tissue composition and fiber orientation derived from clinically feasible QBI at 3T...
April 24, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28438710/a-purpose-built-neck-coil-for-black-blood-dante-prepared-carotid-artery-imaging-at-7t
#12
Konstantinos Papoutsis, Linqing Li, Jamie Near, Stephen Payne, Peter Jezzard
Atherosclerotic plaques in the bifurcation of the carotid arteries can pose a significant health risk due to possible plaque rupture and subsequent stroke. The assessment of plaques, and evaluation of the risk they pose, can be performed with Black-Blood (BB) vessel wall magnetic resonance imaging. However, resolution at standard clinical field strengths (up to 3T) is limited, hampering reliable assessment and diagnosis. The aim of this study was to investigate the benefits of 7T MRI using a BB application that has been successful at clinical field strengths...
April 22, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28438709/characterization-of-high-resolution-gradient-echo-and-spin-echo-epi-for-fmri-in-the-human-visual-cortex-at-7t
#13
Catarina Rua, Mauro Costagli, Mark R Symms, Laura Biagi, Graziella Donatelli, Mirco Cosottini, Alberto Del Guerra, Michela Tosetti
The increased signal-to-noise ratio (SNR) offered by functional Magnetic Resonance Imaging (fMRI) at 7T allows the acquisition of functional data at sub-millimetric spatial resolutions. However, simply reducing partial volume effects is not sufficient to precisely localize task-induced activation due to the indirect mechanisms that relate brain function and the changes in the measured signal. In this work T2* and T2 weighted Echo Planar Imaging (EPI) schemes based on Gradient Recalled Echo (GRE) and Spin Echo (SE) were evaluated in terms of temporal SNR, percent signal change, contrast to noise ratio (CNR), activation volume, and sensitivity and specificity to gray matter...
April 22, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28438713/effects-of-arterial-input-function-selection-on-kinetic-parameters-in-brain-dynamic-contrast-enhanced-mri
#14
Vera C Keil, Burkhard Mädler, Jürgen Gieseke, Rolf Fimmers, Elke Hattingen, Hans H Schild, Dariusch R Hadizadeh
PURPOSE: Kinetic parameters derived from dynamic contrast-enhanced MRI (DCE-MRI) were suggested as a possible instrument for multi-parametric lesion characterization, but have not found their way into clinical practice yet due to inconsistent results. The quantification is heavily influenced by the definition of an appropriate arterial input functions (AIF). Regarding brain tumor DCE-MRI, there are currently several co-existing methods to determine the AIF frequently including different brain vessels as sources...
April 21, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28438711/can-transverse-relaxation-rates-in-deep-gray-matter-be-approximated-from-functional-and-t2-weighted-flair-scans-for-relative-brain-iron-quantification
#15
Benjamín Garzón, Rouslan Sitnikov, Lars Bäckman, Grégoria Kalpouzos
Alterations in iron concentration in certain deep gray matter regions are known to occur in aging and several clinical conditions. In vivo measurements of R2(∗) transverse relaxation rates and quantitative susceptibility mapping (QSM) have been shown to be strongly correlated with iron concentration in tissue, but their calculation requires the acquisition of a multi-echo gradient recalled echo sequence (MGRE). In the current study, we examined the feasibility of approximating R2(∗) rates using metrics derived from fMRI-EPI and T2-weighted FLAIR images, which are widely available...
April 21, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28433503/mr-fingerprinting-reconstruction-with-kalman-filter
#16
Xiaodi Zhang, Zechen Zhou, Shiyang Chen, Shuo Chen, Rui Li, Xiaoping Hu
Magnetic resonance fingerprinting (MR fingerprinting or MRF) is a newly introduced quantitative magnetic resonance imaging technique, which enables simultaneous multi-parameter mapping in a single acquisition with improved time efficiency. The current MRF reconstruction method is based on dictionary matching, which may be limited by the discrete and finite nature of the dictionary and the computational cost associated with dictionary construction, storage and matching. In this paper, we describe a reconstruction method based on Kalman filter for MRF, which avoids the use of dictionary to obtain continuous MR parameter measurements...
April 19, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28414052/spiral-mr-fingerprinting-at-7t-with-simultaneous-b1-estimation
#17
Guido Buonincontri, Rolf F Schulte, Mirco Cosottini, Michela Tosetti
Magnetic resonance fingerprinting is an efficient, new approach for quantitative imaging with MR. We aimed to extend this technique to cases with B1+ inhomogeneities within the imaging volume. Previous approaches have used abrupt changes in flip angles to estimate the B1+ field simultaneously with T1 and T2, using a Cartesian approach in a small-animal scanner at 4.7T. Here, we evaluated whether a similar approach would be suitable for imaging human brains using spiral readouts with a 7T scanner. We found that our modified scheme could significantly reduce the adverse effects of B1+ inhomogeneities even in extreme cases, reducing both the bias and the variance in T2 estimations by an order of magnitude when compared to literature methods...
April 13, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28412455/effects-of-rf-pulse-profile-and-intra-voxel-phase-dispersion-on-mr-fingerprinting-with-balanced-ssfp-readout
#18
Su-Chin Chiu, Te-Ming Lin, Jyh-Miin Lin, Hsiao-Wen Chung, Cheng-Wen Ko, Martin Büchert, Michael Bock
PURPOSE: To investigate possible errors in T1 and T2 quantification via MR fingerprinting with balanced steady-state free precession readout in the presence of intra-voxel phase dispersion and RF pulse profile imperfections, using computer simulations based on Bloch equations. MATERIALS AND METHODS: A pulse sequence with TR changing in a Perlin noise pattern and a nearly sinusoidal pattern of flip angle following an initial 180-degree inversion pulse was employed...
April 13, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28391061/rf-slice-profile-effects-in-magnetic-resonance-fingerprinting
#19
Taehwa Hong, Dongyeob Han, Min-Oh Kim, Dong-Hyun Kim
The radio frequency (RF) slice profile effects on T1 and T2 estimation in magnetic resonance fingerprinting (MRF) are investigated with respect to time-bandwidth product (TBW), flip angle (FA) level and field inhomogeneities. Signal evolutions are generated incorporating the non-ideal slice selective excitation process using Bloch simulation and matched to the original dictionary with and without the non-ideal slice profile taken into account. For validation, phantom and in vivo experiments are performed at 3T...
April 5, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28377304/longitudinal-mri-evaluation-of-neuroprotective-effects-of-pharmacologically-induced-hypothermia-in-experimental-ischemic-stroke
#20
Silun Wang, Xiaohuan Gu, Ramesh Paudyal, Ling Wei, Thomas A Dix, Shan P Yu, Xiaodong Zhang
Pharmacologically induced hypothermia (PIH) shows promising neuroprotective effects after stroke insult. However, the dynamic evolution of stroke infarct during the hypothermic therapy has not been understood very well. In the present study, MRI was utilized to longitudinally characterize the infarct evolution in a mouse model of ischemic stroke treated by PIH using the neurotensin agonist HPI201. Adult male C57BL/6 mice underwent permanent occlusion of the right middle cerebra artery (MCA). Each animal received a vehicle or HPI201 intraperitoneal injection...
April 2, 2017: Magnetic Resonance Imaging
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