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Low field MRI

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https://www.readbyqxmd.com/read/28164362/mri-based-transfer-function-determination-for-the-assessment-of-implant-safety
#1
J P Tokaya, A J E Raaijmakers, P R Luijten, J F Bakker, C A T van den Berg
PURPOSE: We introduce a new MR-based method to determine the transfer function (TF) for radiofrequency (RF) safety assessment of active implantable medical devices. Transfer functions are implant-specific measures that relate the incident tangential electric field on an (elongated) implant to a scattered electric field at its tip. The proposed method allows for TF determination with a high spatial resolution in relatively fast measurements without requiring dedicated bench setups from MRI images...
February 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28161319/biophysical-and-neural-basis-of-resting-state-functional-connectivity-evidence-from-non-human-primates
#2
REVIEW
Li Min Chen, Pai-Feng Yang, Feng Wang, Arabinda Mishra, Zhaoyue Shi, Ruiqi Wu, Tung-Lin Wu, George H Wilson, Zhaohua Ding, John C Gore
Functional MRI (fMRI) has evolved from simple observations of regional changes in MRI signals caused by cortical activity induced by a task or stimulus, to task-free acquisitions of images in a resting state. Such resting state signals contain low frequency fluctuations which may be correlated between voxels, and strongly correlated regions are deemed to reflect functional connectivity within synchronized circuits. Resting state functional connectivity (rsFC) measures have been widely adopted by the neuroscience community, and are being used and interpreted as indicators of intrinsic neural circuits and their functional states in a broad range of applications, both basic and clinical...
February 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28152435/nmr-spin-lock-induced-crossing-slic-dispersion-and-long-lived-spin-states-of-gaseous-propane-at-low-magnetic-field-0-05t
#3
Danila A Barskiy, Oleg G Salnikov, Alexey S Romanov, Matthew A Feldman, Aaron M Coffey, Kirill V Kovtunov, Igor V Koptyug, Eduard Y Chekmenev
When parahydrogen reacts with propylene in low magnetic fields (e.g., 0.05T), the reaction product propane develops an overpopulation of pseudo-singlet nuclear spin states. We studied how the Spin-Lock Induced Crossing (SLIC) technique can be used to convert these pseudo-singlet spin states of hyperpolarized gaseous propane into observable magnetization and to detect (1)H NMR signal directly at 0.05T. The theoretical simulation and experimental study of the NMR signal dependence on B1 power (SLIC amplitude) exhibits a well-resolved dispersion, which is induced by the spin-spin couplings in the eight-proton spin system of propane...
January 21, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28152256/accelerated-dual-venc-4d-flow-mri-for-neurovascular-applications
#4
Susanne Schnell, Sameer A Ansari, Can Wu, Julio Garcia, Ian G Murphy, Ozair A Rahman, Amir A Rahsepar, Maria Aristova, Jeremy D Collins, James C Carr, Michael Markl
PURPOSE: To improve velocity-to-noise ratio (VNR) and dynamic velocity range of 4D flow magnetic resonance imaging (MRI) by using dual-velocity encoding (dual-venc) with k-t generalized autocalibrating partially parallel acquisition (GRAPPA) acceleration. MATERIALS AND METHODS: A dual-venc 4D flow MRI sequence with k-t GRAPPA acceleration was developed using a shared reference scan followed by three-directional low- and high-venc scans (repetition time / echo time / flip angle = 6...
February 2, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28116447/localized-n20-component-of-somatosensory-evoked-magnetic-fields-in-frontoparietal-brain-tumor-patients-using-noise-normalized-approaches
#5
Nor Safira Elaina, Aamir Saeed Malik, Wafaa Khazaal Shams, Nasreen Badruddin, Jafri Malin Abdullah, Mohammad Faruque Reza
PURPOSE: To localize sensorimotor cortical activation in 10 patients with frontoparietal tumors using quantitative magnetoencephalography (MEG) with noise-normalized approaches. MATERIAL AND METHODS: Somatosensory evoked magnetic fields (SEFs) were elicited in 10 patients with somatosensory tumors and in 10 control participants using electrical stimulation of the median nerve via the right and left wrists. We localized the N20m component of the SEFs using dynamic statistical parametric mapping (dSPM) and standardized low-resolution brain electromagnetic tomography (sLORETA) combined with 3D magnetic resonance imaging (MRI)...
January 23, 2017: Clinical Neuroradiology
https://www.readbyqxmd.com/read/28111824/on-the-transmit-field-inhomogeneity-correction-of-relaxation-compensated-amide-and-noe-cest-effects-at-7%C3%A2-t
#6
Vitaliy Khlebnikov, Johannes Windschuh, Jeroen C W Siero, Moritz Zaiss, Peter R Luijten, Dennis W J Klomp, Hans Hoogduin
High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B1 inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST. In this work, two B1 correction algorithms for the most studied CEST effects, amide-CEST and nuclear Overhauser enhancement (NOE), were analyzed...
January 23, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28094419/postoperative-computed-tomography-and-low-field-magnetic-resonance-imaging-findings-in-dogs-with-degenerative-lumbosacral-stenosis-treated-by-dorsal-laminectomy
#7
Martin Rapp, Charles J Ley, Kerstin Hansson, Lennart Sjöström
OBJECTIVES: To describe postoperative computed tomography (CT) and magnetic resonance imaging (MRI) findings in dogs with degenerative lumbosacral stenosis (DLSS) treated by dorsal laminectomy and partial discectomy. METHODS: Prospective clinical case study of dogs diagnosed with and treated for DLSS. Surgical and clinical findings were described. Computed tomography and low field MRI findings pre- and postoperatively were described and graded. Clinical, CT and MRI examinations were performed four to 18 months after surgery...
January 17, 2017: Veterinary and Comparative Orthopaedics and Traumatology: V.C.O.T
https://www.readbyqxmd.com/read/28081157/simultaneous-quantitative-mri-mapping-of-t1-t2-and-magnetic-susceptibility-with-multi-echo-mp2rage
#8
Riccardo Metere, Tobias Kober, Harald E Möller, Andreas Schäfer
The knowledge of relaxation times is essential for understanding the biophysical mechanisms underlying contrast in magnetic resonance imaging. Quantitative experiments, while offering major advantages in terms of reproducibility, may benefit from simultaneous acquisitions. In this work, we demonstrate the possibility of simultaneously recording relaxation-time and susceptibility maps with a prototype Multi-Echo (ME) Magnetization-Prepared 2 RApid Gradient Echoes (MP2RAGE) sequence. T1 maps can be obtained using the MP2RAGE sequence, which is relatively insensitive to inhomogeneities of the radio-frequency transmit field, [Formula: see text]...
2017: PloS One
https://www.readbyqxmd.com/read/28079398/feasibility-evaluation-of-diffusion-weighted-imaging-using-an-integrated-mri-radiotherapy-system-for-response-assessment-to-neoadjuvant-therapy-in-rectal-cancer
#9
Narek Shaverdian, Yingli Yang, Peng Hu, Steven Hart, Ke Sheng, James Lamb, Minsong Cao, Nzhde Agazaryan, David Thomas, Michael Steinberg, Daniel A Low, Percy Lee
OBJECTIVES: To evaluate the feasibility of on-board DWI with an integrated low-field MRI-radiotherapy system to assess responses to neoadjuvant chemoradiation (NAC) in rectal cancer. METHODS: A spin echo-based planar imaging diffusion sequence on a 0.35 T MRI-radiotherapy system was acquired over the course of NAC. The apparent diffusion coefficients (ADC) from the tumor region of interest (ROIs) were calculated. A functional diffusion map (fDM) was created showing a pixel-wise ADC analysis of the ROI over the course of treatment...
January 12, 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/28074903/alterations-in-the-brain-adenosine-metabolism-cause-behavioral-and-neurological-impairment-in-ada-deficient-mice-and-patients
#10
Aisha V Sauer, Raisa Jofra Hernandez, Francesca Fumagalli, Veronica Bianchi, Pietro L Poliani, Chiara Dallatomasina, Elisa Riboni, Letterio S Politi, Antonella Tabucchi, Filippo Carlucci, Miriam Casiraghi, Nicola Carriglio, Manuela Cominelli, Carlo Alberto Forcellini, Federica Barzaghi, Francesca Ferrua, Fabio Minicucci, Stefania Medaglini, Letizia Leocani, Giancarlo la Marca, Lucia D Notarangelo, Chiara Azzari, Giancarlo Comi, Cristina Baldoli, Sabrina Canale, Maria Sessa, Patrizia D'Adamo, Alessandro Aiuti
Adenosine Deaminase (ADA) deficiency is an autosomal recessive variant of severe combined immunodeficiency (SCID) caused by systemic accumulation of ADA substrates. Neurological and behavioral abnormalities observed in ADA-SCID patients surviving after stem cell transplantation or gene therapy represent an unresolved enigma in the field. We found significant neurological and cognitive alterations in untreated ADA-SCID patients as well as in two groups of patients after short- and long-term enzyme replacement therapy with PEG-ADA...
January 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28053326/scanning-the-horizon-towards-transparent-and-reproducible-neuroimaging-research
#11
Russell A Poldrack, Chris I Baker, Joke Durnez, Krzysztof J Gorgolewski, Paul M Matthews, Marcus R Munafò, Thomas E Nichols, Jean-Baptiste Poline, Edward Vul, Tal Yarkoni
Functional neuroimaging techniques have transformed our ability to probe the neurobiological basis of behaviour and are increasingly being applied by the wider neuroscience community. However, concerns have recently been raised that the conclusions that are drawn from some human neuroimaging studies are either spurious or not generalizable. Problems such as low statistical power, flexibility in data analysis, software errors and a lack of direct replication apply to many fields, but perhaps particularly to functional MRI...
February 2017: Nature Reviews. Neuroscience
https://www.readbyqxmd.com/read/28048790/su-f-j-112-clinical-feasibility-test-of-an-rf-pulse-based-mri-method-for-the-quantitative-fat-water-segmentation
#12
S Yee, J Wloch, M Pirkola
PURPOSE: Quantitative fat-water segmentation is important not only because of the clinical utility of fat-suppressed MRI images in better detecting lesions of clinical significance (in the midst of bright fat signal) but also because of the possible physical need, in which CT-like images based on the materials' photon attenuation properties may have to be generated from MR images; particularly, as in the case of MR-only radiation oncology environment to obtain radiation dose calculation or as in the case of hybrid PET/MR modality to obtain attenuation correction map for the quantitative PET reconstruction...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048364/we-fg-207a-01-introduction-to-dedicated-breast-ct-early-studies
#13
S Vedantham
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048141/su-f-j-153-acr-mri-phantom-test-on-a-1-5t-mr-simulator-with-flexible-coils-setting-and-performance-comparison-to-volumetric-head-coil-setting
#14
J Yuan, O Wong, K Cheung, S Yu
PURPOSE: To accommodate head-and-neck (HN) RT simulation scan with immobilization, sub-optimized flexible radiofrequency coils have to be used on an MR-sim rather than a volumetric head coil for diagnostic radiological (DR) applications. In this study, we present and compare ACR MRI phantom test with flexible coils setting (RT-setting) and volumetric head coil setting (DR-setting). METHODS: Two 8-channel array coils were wrapped close to an ACR MRI phantom placed on a flat couch-top in RT-setting for acquisition...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048119/su-f-t-102-automatic-curation-for-a-scalable-registry-using-machine-learning
#15
D Ruan, W Shao, J Wong, D Veruttipong, M Steinberg, D Low, P Kupelian
PURPOSE: growing partnership and contributors to registry efforts an efficient way to perform data integration, de-duplication, and cleansing, amongst other tasks. This project aims to develop an automatic curation module to discover, clean, and transform new data, and semantically integrate them with the composite hosting registry upon de-duplication. METHODS: We have investigated various similarity metrics for various attributes and value types in the registry...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048061/mo-fg-campus-jep2-01-4d-mri-with-3d-radial-sampling-and-self-gating-based-k-space-sorting-image-quality-improvement-by-slab-selective-excitation
#16
Z Deng, W Yang, J Pang, R Tuli, X Bi, B Hakimian, B Fraass, D Li, Z Fan
PURPOSE: A recent 4D MRI technique based on 3D radial sampling and self-gating-based K-space sorting has shown promising results in characterizing respiratory motion. However due to continuous acquisition and potentially drastic k-space undersampling resultant images could suffer from low blood-to-tissue contrast and streaking artifacts. In this study 3D radial sampling with slab-selective excitation (SS) was proposed in attempt to enhance blood-to-tissue contrast by exploiting the in-flow effect and to suppress the excess signal from the peripheral structures particularly in the superior-inferior direction...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047811/th-ab-bra-12-experimental-results-from-the-first-high-field-inline-mri-linac
#17
P Keall, B Dong, P Vial, A Walker, K Zhang, J Begg, R Rai, L Holloway, M Barton, S Crozier, G Liney
PURPOSE: The pursuit of real-time image guided radiotherapy using optimal tissue contrast has seen the development of several hybrid MRI-treatment systems, high field and low field, and inline and perpendicular configurations. As part of a new MRI-Linac program, an MRI scanner was integrated with a linear accelerator to enable investigations of a coupled inline MRI-Linac system. This work describes our experimental results from the first high-field inline MRI-Linac. METHODS: A 1...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047787/th-ab-bra-02-automated-triplet-beam-orientation-optimization-for-mri-guided-co-60-radiotherapy
#18
D Nguyen, D Thomas, M Cao, D O'Connor, J Lamb, K Sheng
PURPOSE: MRI guided Co-60 provides daily and intrafractional MRI soft tissue imaging for improved target tracking and adaptive radiotherapy. To remedy the low output limitation, the system uses three Co-60 sources at 120° apart, but using all three sources in planning is considerably unintuitive. We automate the beam orientation optimization using column generation, and then solve a novel fluence map optimization (FMO) problem while regularizing the number of MLC segments. METHODS: Three patients-1 prostate (PRT), 1 lung (LNG), and 1 head-and-neck boost plan (H&NBoost)-were evaluated...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047717/we-fg-207a-02-why-we-need-breast-ct-clinical-perspective
#19
A O'Connell
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047520/we-fg-207a-05-dedicated-breast-ct-as-a-diagnostic-imaging-tool-physics-and-clinical-feasibility
#20
A Karellas
: Mammography-based screening has been a valuable imaging tool for the early detection of non-palpable lesions and has contributed to significant reduction in breast cancer associated mortality. However, the breast imaging community recognizes that mammography is not ideal, and in particular is inferior for women with dense breasts. Also, the 2-D projection of a 3-D organ results in tissue superposition contributing to false-positives. The sensitivity of mammography is breast-density dependent...
June 2016: Medical Physics
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