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Low field MRI

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https://www.readbyqxmd.com/read/29350408/calibration-and-non-orthogonality-correction-of-three-axis-hall-sensors-for-the-monitoring-of-mri-workers-exposure-to-static-magnetic-fields
#1
Antoine Delmas, Lamia Belguerras, Nicolas Weber, Freddy Odille, Cédric Pasquier, Jacques Felblinger, Pierre-André Vuissoz
A Magnetic Resonance Imaging (MRI) scanner uses three different electromagnetic fields (EMF) to produce body images: a static permanent magnetic field (MF), several pulsed magnetic gradients, and a radiofrequency pulse. As a result, any occupation that includes an MRI exposes workers to a strong MF. The World Health Organization has now given the monitoring of occupational EMF exposure a high priority. One design for a low-cost, compact MF exposure monitor (« MR exposimeter ») uses a set of three orthogonally assembled Hall sensors...
January 19, 2018: Bioelectromagnetics
https://www.readbyqxmd.com/read/29330835/international-guidelines-for-groin-hernia-management
#2
(no author information available yet)
INTRODUCTION: Worldwide, more than 20 million patients undergo groin hernia repair annually. The many different approaches, treatment indications and a significant array of techniques for groin hernia repair warrant guidelines to standardize care, minimize complications, and improve results. The main goal of these guidelines is to improve patient outcomes, specifically to decrease recurrence rates and reduce chronic pain, the most frequent problems following groin hernia repair. They have been endorsed by all five continental hernia societies, the International Endo Hernia Society and the European Association for Endoscopic Surgery...
January 12, 2018: Hernia: the Journal of Hernias and Abdominal Wall Surgery
https://www.readbyqxmd.com/read/29330713/low-field-magnetic-resonance-imaging-offers-potential-for-measuring-tibial-component-migration
#3
F F Schröder, N J J Verdonschot, B Ten Haken, A Peters, A J H Vochteloo, D F M Pakvis, R Huis In't Veld
BACKGROUND: Roentgen stereophotogrammetric analysis (RSA) is used to measure early prosthetic migration and to predict future implant failure. RSA has several disadvantages, such as the need for perioperatively inserted tantalum markers. Therefore, this study evaluates low-field MRI as an alternative to RSA. The use of traditional MRI with prostheses induces disturbing metal artifacts which are reduced by low-field MRI. The purpose of this study is to assess the feasibility to use low-field (0...
January 12, 2018: Journal of Experimental Orthopaedics
https://www.readbyqxmd.com/read/29328047/optimal-multichannel-transmission-for-improved-cr-mrept
#4
Gokhan Ariturk, Yusuf Ziya Ider
Magnetic resonance electrical properties tomography (MR-EPT), aiming at reconstructing the EP's at radio frequencies, uses the H<sup>+</sup> field (both magnitude and phase) distribution within the object. One of the MR-EPT algorithms, cr-MREPT, accurately reconstructs the internal tissue boundaries however it faces an artifact which occurs at the regions where the convective field, [ (∂H<sup>+</sup> / ∂x ) - i(∂H<sup>+</sup> / ∂y) i((∂H<sup>+</sup> / ∂x ) - i(∂H<sup>+</sup> / ∂y)) ] , has a low magnitude (at the noise level)...
January 12, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29325943/neurosurgical-care-availability-and-access-in-low-and-middle-income-countries
#5
Maria Punchak, Swagoto Mukhopadhyay, Sonal Sachdev, Ya-Ching Hung, Sophie Peeters, Abbas Rattani, Michael Dewan, Walter D Johnson, Kee B Park
BACKGROUND: An estimated 5 billion people worldwide lack access to basic surgical care. In particular, the vast majority of low- and middle-income countries (LMICs) currently struggle to provide adequate neurosurgical services. Significant barriers exist, including limited access to trained medical, nursing and allied health staff, lack of equipment, and availability of services at reasonable distance and at reasonable cost to patients. An accurate assessment of current neurosurgical capacity in LIMCs is an essential first step in tackling this deficit...
January 8, 2018: World Neurosurgery
https://www.readbyqxmd.com/read/29322101/a-novel-individual-level-morphological-brain-networks-constructing-method-and-its-evaluation-in-pet-and-mr-images
#6
Jiehui Jiang, Hucheng Zhou, Huoqiang Duan, Xin Liu, Chuantao Zuo, Zhemin Huang, Zhihua Yu, Zhuangzhi Yan
Mapping the human brain is one of the great scientific challenges of the 21st century. Brain network analysis is an effective technique based on graph theory that is widely used to investigate network patterns in the human brain. Currently, mapping an individual brain network using a single image has been a hotspot in the field of brain science; techniques, such as the Kullback-Leibler (KL) method, have applications in structural Magnetic Resonance (MR) imaging. However, maintaining an image's intensity, shape, texture and gradient information during feature extraction is very challenging...
December 2017: Heliyon
https://www.readbyqxmd.com/read/29314060/dynamic-field-of-view-imaging-to-increase-temporal-resolution-in-the-early-phase-of-contrast-media-uptake-in-breast-dce-mri-a-feasibility-study
#7
Federico D Pineda, Ty O Easley, Gregory S Karczmar
PURPOSE: To increase diagnostic accuracy of breast MRI by increasing temporal resolution and more accurately sampling the early kinetics of contrast media uptake. We tested the feasibility of accelerating bilateral breast DCE-MRI by reducing the FOV, allowing aliasing, and unfolding the resulting images. METHODS: Previous experience with an 'ultrafast' protocol for bilateral breast DCE-MRI (6s-10s temporal resolution) showed that the number of significantly enhancing voxels is very low in the first 30 to 45 seconds after contrast media injection...
January 3, 2018: Medical Physics
https://www.readbyqxmd.com/read/29302913/principles-and-applications-of-the-balanced-steady-state-free-precession-sequence-in-small-animal-low-field-mri
#8
Mario Ricciardi
Magnetic resonance imaging (MRI) in small animal practice is largely based on classic two-dimensional spin-echo, inversion recovery and gradient-echo sequences which are largely limited by low spatial resolution, especially in low-field (LF)-MRI scanners. Nowadays, however, the availability of volumetric sequences can open new perspectives and enhance the diagnostic potential of this imaging modality. Balanced steady-state free precession (bSSFP) is a three-dimensional gradient-echo sequence in which image contrast is given by the ratio of T2 and T1, resulting in low soft-tissue signal, poor cerebral grey/white matter distinction and a bright signal from free fluid and fat...
January 4, 2018: Veterinary Research Communications
https://www.readbyqxmd.com/read/29289224/a-high-pressure-metallic-core-holder-for-magnetic-resonance-based-on-hastelloy-c
#9
M Shakerian, F Marica, A Afrough, F G Goora, M Li, S Vashaee, B J Balcom
A metallic core holder, fabricated from non-magnetic Hastelloy-C276, has been designed for Magnetic Resonance (MR) and Magnetic Resonance Imaging (MRI) of core plug samples at high pressures and temperatures. Core plug samples, 1.5″ in diameter and 2″ in length, can be tested in the core holder at elevated pressures and temperatures, up to 5000 psi and 80 °C. These are conditions commonly found in petroleum reservoirs. A radio frequency probe, which excites and detects magnetic resonance signals, was placed inside the metal vessel...
December 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29286684/three-dimensional-general-relativistic-magnetohydrodynamic-simulations-of-remnant-accretion-disks-from-neutron-star-mergers-outflows-and-r-process-nucleosynthesis
#10
Daniel M Siegel, Brian D Metzger
The merger of binary neutron stars, or of a neutron star and a stellar-mass black hole, can result in the formation of a massive rotating torus around a spinning black hole. In addition to providing collimating media for γ-ray burst jets, unbound outflows from these disks are an important source of mass ejection and rapid neutron capture (r-process) nucleosynthesis. We present the first three-dimensional general-relativistic magnetohydrodynamic (GRMHD) simulations of neutrino-cooled accretion disks in neutron star mergers, including a realistic equation of state valid at low densities and temperatures, self-consistent evolution of the electron fraction, and neutrino cooling through an approximate leakage scheme...
December 8, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29278548/the-current-place-of-epilepsy-surgery
#11
Jerome Engel
PURPOSE OF REVIEW: Three randomized controlled trials demonstrate that surgical treatment is safe and effective for drug-resistant epilepsy (DRE), yet fewer than 1% of patients are referred for surgery. This is a review of recent trends in surgical referral for DRE, and advances in the field. Reasons for continued underutilization are discussed. RECENT FINDINGS: Recent series indicate no increase in surgical referral for DRE over the past two decades. One study suggests that decreased referrals to major epilepsy centers can be accounted for by increased referrals to low-volume nonacademic hospitals where results are poorer, and complication rates higher...
December 22, 2017: Current Opinion in Neurology
https://www.readbyqxmd.com/read/29250795/sweet-cherry-softening-accompanied-with-moisture-migration-and-loss-during-low-temperature-storage
#12
Danshi Zhu, Jieyu Liang, He Liu, Xuehui Cao, Yonghong Ge, Jianrong Li
BACKGROUND: Hardness is one of the important qualities influencing consumer appeal and marketing of fresh sweet cherry (Prunus avium L.). Moisture loss is one of the main causative factors of cherry softening. In this work, moisture loss and softening process of sweet cherry during postharvest storage at 0 °C and 4 °C were studied. In addition, Low-field 1 H nuclear magnetic resonance (LF-NMR) was used to analyze water distribution and migration in sweet cherry during storage at 4 °C...
December 18, 2017: Journal of the Science of Food and Agriculture
https://www.readbyqxmd.com/read/29249930/effects-of-field-map-distortion-correction-on-resting-state-functional-connectivity-mri
#13
Hiroki Togo, Jaroslav Rokicki, Kenji Yoshinaga, Tatsuhiro Hisatsune, Hiroshi Matsuda, Nobuhiko Haga, Takashi Hanakawa
Magnetic field inhomogeneities cause geometric distortions of echo planar images used for functional magnetic resonance imaging (fMRI). To reduce this problem, distortion correction (DC) with field map is widely used for both task and resting-state fMRI (rs-fMRI). Although DC with field map has been reported to improve the quality of task fMRI, little is known about its effects on rs-fMRI. Here, we tested the influence of field-map DC on rs-fMRI results using two rs-fMRI datasets derived from 40 healthy subjects: one with DC (DC+) and the other without correction (DC-)...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/29244225/combination-of-surface-and-vertical-loop-elements-improves-receive-performance-of-a-human-head-transceiver-array-at-9-4%C3%A2-t
#14
N I Avdievich, I A Giapitzakis, A Pfrommer, T Borbath, A Henning
Ultra-high-field (UHF, ≥7 T) human magnetic resonance imaging (MRI) provides undisputed advantages over low-field MRI (≤3 T), but its development remains challenging because of numerous technical issues, including the low efficiency of transmit (Tx) radiofrequency (RF) coils caused by the increase in tissue power deposition with frequency. Tight-fit human head transceiver (TxRx) arrays improve Tx efficiency in comparison with Tx-only arrays, which are larger in order to fit multi-channel receive (Rx)-only arrays inside...
December 15, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/29210434/nano-confinement-driven-enhanced-magnetic-relaxivity-of-spions-for-targeted-tumor-bioimaging
#15
Tuyen Duong Thanh Nguyen, Arunkumar Pitchaimani, Colin Ferrel, Ravindra Thakkar, Santosh Aryal
Superparamagnetic iron oxide nanoparticles (SPIONs) are highly biocompatible and have a versatile synthetic technique based on coprecipitation, reduction-precipitation, and hydrothermal methods, where Fe3+ and Fe2+ react in aqueous solutions; both these ions are present in our body and have clear metabolic pathways; therefore, they have attracted extensive research interest and development in the field of diagnostic imaging and therapy. However, most SPION-based clinical diagnostic contrast agents are discontinued due to severe pain, low transverse magnetic relaxivity range of 80-180 mM-1 s-1, shorter circulation half-life, and lack of disease specificity...
December 6, 2017: Nanoscale
https://www.readbyqxmd.com/read/29204762/magnetic-resonance-imaging-mri-of-feet-demonstrates-subclinical-inflammatory-joint-disease-in-cutaneous-psoriasis-patients-without-clinical-arthritis
#16
Ashish J Mathew, Paul Bird, Ankan Gupta, Renu George, Debashish Danda
We evaluated inflammation at the small joints of feet in psoriasis patients without clinical arthritis (PsO) as against clinically overt psoriatic arthritis (PsA) patients, using a low field magnet extremity MRI (eMRI). Patients with psoriasis recruited from dermatology and rheumatology clinics of a tertiary care institution in southern India were divided into PsO and PsA groups. Demographic and physical examination details were recorded. Consenting patients underwent non-contrast eMRI of the right foot. Two trained readers scored the MRI parameters of inflammation (synovitis, tenosynovitis, osteitis) using a modification of the PsA magnetic resonance imaging score (PsAMRIS)...
December 4, 2017: Clinical Rheumatology
https://www.readbyqxmd.com/read/29197694/experimental-investigation-of-a-metasurface-resonator-for-in-vivo-imaging-at-1-5%C3%A2-t
#17
Alena V Shchelokova, Alexey P Slobozhanyuk, Paul de Bruin, Irena Zivkovic, Efthymios Kallos, Pavel A Belov, Andrew Webb
In this work, we experimentally demonstrate an increase in the local transmit efficiency of a 1.5 T MRI scanner by using a metasurface formed by an array of brass wires embedded in a high permittivity low loss medium. Placement of such a structure inside the scanner results in strong coupling of the radiofrequency field produced by the body coil with the lowest frequency electromagnetic eigenmode of the metasurface. This leads to spatial redistribution of the near fields with enhancement of the local magnetic field and an increase in the transmit efficiency per square root maximum specific absorption rate in the region-of-interest...
November 22, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/29194732/doppler-ultrasound-triggering-for-cardiac-mri-at-7t
#18
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/29192363/quantitative-and-visual-assessments-toward-potential-sub-msv-or-ultrafast-fdg-pet-using-high-sensitivity-tof-pet-in-pet-mri
#19
Spencer C Behr, Emma Bahroos, Randall A Hawkins, Lorenzo Nardo, Vahid Ravanfar, Emily V Capbarat, Youngho Seo
PURPOSE: Newer high-performance time-of-flight (TOF) positron emission tomography (PET) systems have the capability to preserve diagnostic image quality with low count density, while maintaining a high raw photon detection sensitivity that would allow for a reduction in injected dose or rapid data acquisition. To assess this, we performed quantitative and visual assessments of the PET images acquired using a highly sensitive (23.3 cps/kBq) large field of view (25-cm axial) silicon photomultiplier (SiPM)-based TOF PET (400-ps timing resolution) integrated with 3 T-MRI in comparison to PET images acquired on non-TOF PET/x-ray computed tomography (CT) systems...
November 30, 2017: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/29186760/effects-of-a-60-hz-magnetic-field-of-up-to-50-millitesla-on-human-tremor-and-eeg-a-pilot-study
#20
(no author information available yet)
Humans are surrounded by sources of daily exposure to power-frequency (60 Hz in North America) magnetic fields (MFs). Such time-varying MFs induce electric fields and currents in living structures which possibly lead to biological effects. The present pilot study examined possible extremely low frequency (ELF) MF effects on human neuromotor control in general, and physiological postural tremor and electroencephalography (EEG) in particular. Since the EEG cortical mu-rhythm (8-12 Hz) from the primary motor cortex and physiological tremor are related, it was hypothesized that a 60 Hz MF exposure focused on this cortical region could acutely modulate human physiological tremor...
November 24, 2017: International Journal of Environmental Research and Public Health
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