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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/29222852/free-breathing-whole-heart-3d-cine-magnetic-resonance-imaging-with-prospective-respiratory-motion-compensation
#1
Mehdi H Moghari, Ashita Barthur, Maria E Amaral, Tal Geva, Andrew J Powell
PURPOSE: To develop and validate a new prospective respiratory motion compensation algorithm for free-breathing whole-heart 3D cine steady-state free precession (SSFP) imaging. METHODS: In a 3D cine SSFP sequence, 4 excitations per cardiac cycle are re-purposed to prospectively track heart position. Specifically, their 1D image is reconstructed and routed into the scanner's standard diaphragmatic navigator processing system. If all 4 signals are in end-expiration, cine image data from the entire cardiac cycle is accepted for image reconstruction...
December 8, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29215150/mri-monitoring-of-focused-ultrasound-sonications-near-metallic-hardware
#2
Hans Weber, Pejman Ghanouni, Aurea Pascal-Tenorio, Kim Butts Pauly, Brian A Hargreaves
PURPOSE: To explore the temperature-induced signal change in two-dimensional multi-spectral imaging (2DMSI) for fast thermometry near metallic hardware to enable MR-guided focused ultrasound surgery (MRgFUS) in patients with implanted metallic hardware. METHOD: 2DMSI was optimized for temperature sensitivity and applied to monitor focus ultrasound surgery (FUS) sonications near metallic hardware in phantoms and ex vivo porcine muscle tissue. Further, we evaluated its temperature sensitivity for in vivo muscle in patients without metallic hardware...
December 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29215148/31-p-t2-s-of-phosphomonoesters-phosphodiesters-and-inorganic-phosphate-in-the-human-brain-at-7t
#3
Wybe J M van der Kemp, Dennis W J Klomp, Jannie P Wijnen
PURPOSE: To determine the phosphorus-31 T2 s of phosphomonoesters, phosphodiesters, and inorganic phosphate in the healthy human brain at 7T. METHODS: A 3D chemical shift imaging multi-echo sequence with composite block pulses for refocusing was used to measure one free induction decay (FID) and seven full echoes with an echo spacing of 45 ms on the brain of nine healthy volunteers (age range 22-45 years; average age 27 ± 8 years). Spectral fitting was used to determine the change in metabolic signal amplitude with echo time...
December 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29215137/frequency-and-phase-correction-for-multiplexed-edited-mrs-of-gaba-and-glutathione
#4
Mark Mikkelsen, Muhammad G Saleh, Jamie Near, Kimberly L Chan, Tao Gong, Ashley D Harris, Georg Oeltzschner, Nicolaas A J Puts, Kim M Cecil, Iain D Wilkinson, Richard A E Edden
PURPOSE: Detection of endogenous metabolites using multiplexed editing substantially improves the efficiency of edited magnetic resonance spectroscopy. Multiplexed editing (i.e., performing more than one edited experiment in a single acquisition) requires a tailored, robust approach for correction of frequency and phase offsets. Here, a novel method for frequency and phase correction (FPC) based on spectral registration is presented and compared against previously presented approaches...
December 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29205480/a-z-gradient-array-for-simultaneous-multi-slice-excitation-with-a-single-band-rf-pulse
#5
Koray Ertan, Soheil Taraghinia, Alireza Sadeghi, Ergin Atalar
PURPOSE: Multi-slice radiofrequency (RF) pulses have higher specific absorption rates, more peak RF power, and longer pulse durations than single-slice RF pulses. Gradient field design techniques using a z-gradient array are investigated for exciting multiple slices with a single-band RF pulse. THEORY AND METHODS: Two different field design methods are formulated to solve for the required current values of the gradient array elements for the given slice locations...
December 4, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29205477/quantitative-comparison-of-delayed-ferumoxytol-t1-enhancement-with-immediate-gadoteridol-enhancement-in-high-grade-gliomas
#6
Andrea Horváth, Csanad G Varallyay, Daniel Schwartz, Gerda B Toth, Joao P Netto, Ramon Barajas, Péter Várallyay, László Szidonya, Jenny Firkins, Emily Youngers, Rongwei Fu, Prakash Ambady, Péter Bogner, Edward A Neuwelt
PURPOSE: Delayed ferumoxytol enhancement on T1 -weighted images appears visually similar to gadoteridol enhancement. The purpose of this study was to quantitatively compare ferumoxytol T1 enhancement to gadoteridol enhancement with an objective, semi-automated method. METHODS: 206 sets of post-gadoteridol and 24 h post-ferumoxytol T1 -weighted scans from 58 high grade glioma patients were analyzed (9 pre-chemoradiation, 111 < 90 days post-chemoradiation, 21 > 90 days post-chemoradiation, 65 post-bevacizumab scans)...
December 4, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29194739/transverse-signal-decay-under-the-weak-field-approximation-theory-and-validation
#7
Avery J L Berman, G Bruce Pike
PURPOSE: To derive an expression for the transverse signal time course from systems in the motional narrowing regime, such as water diffusing in blood. This was validated in silico and experimentally with ex vivo blood samples. METHODS: A closed-form solution (CFS) for transverse signal decay under any train of refocusing pulses was derived using the weak field approximation. The CFS was validated via simulations of water molecules diffusing in the presence of spherical perturbers, with a range of sizes and under various pulse sequences...
December 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29194738/cardiac-mr-elastography-using-reduced-fov-single-shot-spin-echo-epi
#8
Yi Sui, Shivaram Poigai Arunachalam, Arvin Arani, Joshua D Trzasko, Phillip M Young, James F Glockner, Kevin J Glaser, David S Lake, Kiaran P McGee, Armando Manduca, Phillip J Rossman, Richard L Ehman, Philip A Araoz
PURPOSE: To implement a reduced field of view (rFOV) technique for cardiac MR elastography (MRE) and to demonstrate the improvement in image quality of both magnitude images and post-processed MRE stiffness maps compared to the conventional full field of view (full-FOV) acquisition. METHODS: With Institutional Review Board approval, 17 healthy volunteers underwent both full-FOV and rFOV cardiac MRE scans using 140-Hz vibrations. Two cardiac radiologists blindly compared the magnitude images and stiffness maps and graded the images based on several image quality attributes using a 5-point ordinal scale...
December 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29194734/in-vivo-characterization-of-brain-ultrashort-t2-components
#9
Tanguy Boucneau, Peng Cao, Shuyu Tang, Misung Han, Duan Xu, Roland G Henry, Peder E Z Larson
PURPOSE: Recent nuclear magnetic resonance and MRI studies have measured a fast-relaxing signal component with T2∗<1 ms in white matter and myelin extracts. In ex vivo studies, evidence suggests that a large fraction of this component directly arises from bound protons in the myelin phospholipid membranes. Based on these results, this ultrashort-T2 component in nervous tissue is a new potential imaging biomarker of myelination, which plays a critical role in neuronal signal conduction across the brain and loss or degradation of myelin is a key feature of many neurological disorders...
December 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29194732/doppler-ultrasound-triggering-for-cardiac-mri-at-7t
#10
F Kording, C Ruprecht, B Schoennagel, K Fehrs, J Yamamura, G Adam, J Goebel, K Nassenstein, S Maderwald, H H Quick, O Kraff
PURPOSE: A prerequisite for cardiac MR (CMR) imaging is adequate synchronization of image acquisition with the cardiac cycle. Electrocardiogram triggering may be hampered by electromagnetic interferences at high field strength. The purpose of this work is to evaluate the feasibility of Doppler ultrasound triggering for CMR image synchronization at 7T ultra-high-field MRI. METHODS: A custom-built Doppler ultrasound (DUS) trigger device was developed. Magnetic resonance compatibility was evaluated using E- and H-field probes and flip angle maps prior to the study...
December 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29194727/diminished-cerebral-oxygen-extraction-and-metabolic-rate-in-sickle-cell-disease-using-t2-relaxation-under-spin-tagging-mri
#11
Adam M Bush, Thomas D Coates, John C Wood
PURPOSE: T2 MRI oximetry can noninvasively determine oxygen saturation (Y) but requires empirical MR calibration models to convert the measured blood transverse relaxation (T2b ) into Y. The accuracy of existing T2b models in the presence of blood disorders such as sickle cell disease (SCD) remains unknown. METHODS: A Carr Purcell Meiboom Gill T2 preparation sequence was used to make 83 whole blood measurements from 11 subjects with SCD to derive an ex vivo sickle hemoglobin (HbS) T2b model...
December 1, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193250/design-of-universal-parallel-transmit-refocusing-kt-point-pulses-and-application-to-3d-t2-weighted-imaging-at-7t
#12
Vincent Gras, Franck Mauconduit, Alexandre Vignaud, Alexis Amadon, Denis Le Bihan, Tony Stöcker, Nicolas Boulant
PURPOSE: T2 -weighted sequences are particularly sensitive to the radiofrequency (RF) field inhomogeneity problem at ultra-high-field because of the errors accumulated by the imperfections of the train of refocusing pulses. As parallel transmission (pTx) has proved particularly useful to counteract RF heterogeneities, universal pulses were recently demonstrated to save precious time and computational efforts by skipping B1 calibration and online RF pulse tailoring. Here, we report a universal RF pulse design for non-selective refocusing pulses to mitigate the RF inhomogeneity problem at 7T in turbo spin-echo sequences with variable flip angles...
November 29, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193231/using-mri-cell-tracking-to-monitor-immune-cell-recruitment-in-response-to-a-peptide-based-cancer-vaccine
#13
Marie-Laurence Tremblay, Christa Davis, Chris V Bowen, Olivia Stanley, Cathryn Parsons, Genevieve Weir, Mohan Karkada, Marianne M Stanford, Kimberly D Brewer
PURPOSE: MRI cell tracking can be used to monitor immune cells involved in the immunotherapy response, providing insight into the mechanism of action, temporal progression of tumor growth, and individual potency of therapies. To evaluate whether MRI could be used to track immune cell populations in response to immunotherapy, CD8+ cytotoxic T cells, CD4+ CD25+ FoxP3+ regulatory T cells, and myeloid-derived suppressor cells were labeled with superparamagnetic iron oxide particles. METHODS: Superparamagnetic iron oxide-labeled cells were injected into mice (one cell type/mouse) implanted with a human papillomavirus-based cervical cancer model...
November 29, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193380/optimization-and-validation-of-accelerated-golden-angle-radial-sparse-mri-reconstruction-with-self-calibrating-grappa-operator-gridding
#14
Thomas Benkert, Ye Tian, Chenchan Huang, Edward V R DiBella, Hersh Chandarana, Li Feng
PURPOSE: Golden-angle radial sparse parallel (GRASP) MRI reconstruction requires gridding and regridding to transform data between radial and Cartesian k-space. These operations are repeatedly performed in each iteration, which makes the reconstruction computationally demanding. This work aimed to accelerate GRASP reconstruction using self-calibrating GRAPPA operator gridding (GROG) and to validate its performance in clinical imaging. METHODS: GROG is an alternative gridding approach based on parallel imaging, in which k-space data acquired on a non-Cartesian grid are shifted onto a Cartesian k-space grid using information from multicoil arrays...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193340/template-based-field-map-prediction-for-rapid-whole-brain-b0-shimming
#15
Yuhang Shi, S Johanna Vannesjo, Karla L Miller, Stuart Clare
PURPOSE: In typical MRI protocols, time is spent acquiring a field map to calculate the shim settings for best image quality. We propose a fast template-based field map prediction method that yields near-optimal shims without measuring the field. METHODS: The template-based prediction method uses prior knowledge of the B0 distribution in the human brain, based on a large database of field maps acquired from different subjects, together with subject-specific structural information from a quick localizer scan...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193339/a-rapid-t1-mapping-method-for-assessment-of-murine-kidney-viability-using-dynamic-manganese-enhanced-magnetic-resonance-imaging
#16
Kai Jiang, Hui Tang, Prasanna K Mishra, Slobodan I Macura, Lilach O Lerman
PURPOSE: Dynamic manganese-enhanced MRI (MEMRI) allows assessment of tissue viability by tracing manganese uptake. We aimed to develop a rapid T1 mapping method for dynamic MEMRI to facilitate assessments of murine kidney viability. METHODS: A multi-slice saturation recovery fast spin echo (MSRFSE) was developed, validated, and subsequently applied in dynamic MEMRI at 16.4T on ischemic mouse kidneys after 4 weeks of unilateral renal artery stenosis (RAS). Baseline T1 values and post-contrast R1 (1/T1 ) changes were measured in cortex (CO), outer (OSOM), inner (ISOM) strips of outer medulla, and inner medulla (IM)...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193307/approaching-ultimate-intrinsic-specific-absorption-rate-in-radiofrequency-shimming-using-high-permittivity-materials-at-7-tesla
#17
Gillian G Haemer, Manushka Vaidya, Christopher M Collins, Daniel K Sodickson, Graham C Wiggins, Riccardo Lattanzi
PURPOSE: The aim of this study was to evaluate the effect of integrated high-permittivity materials (HPMs) on excitation homogeneity and global specific absorption rate (SAR) for transmit arrays at 7T. METHODS: A rapid electrodynamic simulation framework was used to calculate L-curves associated with excitation of a uniform 2D profile in a dielectric sphere. We used ultimate intrinsic SAR as an absolute performance reference to compare different transmit arrays in the presence and absence of a layer of HPM...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193306/artificial-neural-networks-for-stiffness-estimation-in-magnetic-resonance-elastography
#18
Matthew C Murphy, Armando Manduca, Joshua D Trzasko, Kevin J Glaser, John Huston, Richard L Ehman
PURPOSE: To investigate the feasibility of using artificial neural networks to estimate stiffness from MR elastography (MRE) data. METHODS: Artificial neural networks were fit using model-based training patterns to estimate stiffness from images of displacement using a patch size of ∼1 cm in each dimension. These neural network inversions (NNIs) were then evaluated in a set of simulation experiments designed to investigate the effects of wave interference and noise on NNI accuracy...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193299/improved-parallel-image-reconstruction-using-feature-refinement
#19
Jing Cheng, Sen Jia, Leslie Ying, Yuanyuan Liu, Shanshan Wang, Yanjie Zhu, Ye Li, Chao Zou, Xin Liu, Dong Liang
PURPOSE: The aim of this study was to develop a novel feature refinement MR reconstruction method from highly undersampled multichannel acquisitions for improving the image quality and preserve more detail information. THEORY AND METHODS: The feature refinement technique, which uses a feature descriptor to pick up useful features from residual image discarded by sparsity constrains, is applied to preserve the details of the image in compressed sensing and parallel imaging in MRI (CS-pMRI)...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/29193288/characterization-of-tumor-vascular-permeability-using-natural-dextrans-and-cest-mri
#20
Yuguo Li, Yuan Qiao, Hanwei Chen, Renyuan Bai, Verena Staedtke, Zheng Han, Jiadi Xu, Kannie W Y Chan, Nirbhay Yadav, Jeff W M Bulte, Shibin Zhou, Peter C M van Zijl, Guanshu Liu
PURPOSE: To investigate the use of natural dextrans as nano-sized chemical exchange saturation transfer (CEST) MRI probes for characterizing size-dependent tumor vascular permeability. METHODS: Dextrans of different molecular weight (10, 70, 150, and 2000 kD) were characterized for their CEST contrast. Mice (N = 5) bearing CT26 subcutaneous colon tumors were injected intravenously with 10 kD (D10, 6 nm) and 70 kD (D70, 12 nm) dextran at a dose of 375 mg/kg...
November 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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