نتایج جستجو برای: field mri

تعداد نتایج: 885441  

2013
Mark Ison Eva Dittrich René Donner Gregor Kasprian Daniela Prayer Georg Langs

Abstract. Fetal magnetic resonance imaging (MRI) is a rapidly growing field of research for its potential to study brain development in utero. However, in contrast to adult studies automatic brain extraction and orientation is not yet solved, but remains challenging in wide field of view raw fetal MRI volumes. This has limited research to small scale studies. This paper presents an automatic fe...

Journal: :Journal of magnetism and magnetic materials 2010
P Cantillon-Murphy L L Wald E Adalsteinsson M Zahn

In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, τ. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency,...

Journal: :Journal of magnetic resonance 2014
Nicholas W Halpern-Manners Daniel J Kennedy David R Trease Thomas Z Teisseyre Nicolas S Malecek Alexander Pines Vikram S Bajaj

Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) may be employed as noninvasive measurements yielding detailed information about the chemical and physical parameters that define microscale flows. Despite these advantages, magnetic resonance has been difficult to combine with microfluidics, largely due to its low sensitivity when detecting small sample volumes and the diffic...

Journal: :Magnetic resonance imaging 2003
Arvind K Venkatesh Adelaide X Zhang Joey Mansour Lyubov Kubatina Chang Hyun Oh Gregory Blasche M Selim Unlü Dilip Balamore Ferenc A Jolesz Bennett B Goldberg Mitchell S Albert

In hyperpolarized (HP) noble-gas magnetic resonance imaging, large nuclear spin polarizations, about 100,000 times that ordinarily obtainable at thermal equilibrium, are created in 3He and 129Xe. The enhanced signal that results can be employed in high-resolution MRI studies of void spaces such as in the lungs. In HP gas MRI the signal-to-noise ratio (SNR) depends only weakly on the static magn...

2004
G. Giovannetti R. Francesconi L. Landini V. Viti M. F. Santarelli V. Positano A. Benassi

The main goal of this research was to demonstrate the utility of using a quadrature birdcage coil in lowpass version for magnetic resonance imaging (MRI) in open scanner at very low static field. When used in horizontal bore MRI systems, the birdcage coil is able to produce circular polarized field using quadrature excitation, thus reaching SNR improvement of 2 as maximum value. The birdcage co...

2015
Yiqun Xue Jinhu Xiong

Magnetic source MRI (msMRI) has been developed recently for direct detections of neuronal magnetic fields to map brain activity. However, whether MRI can be used for direct detection of neuronal activity is a matter of debate. Controversial theoretical and experimental results have been reported. In this work, theoretical modeling and experimental validation have been presented to demonstrate t...

2008
Geoffroy Lesur Gordon I. Ogilvie

The magnetorotational instability (MRI) is believed to be an efficient way to transport angular momentum in accretion discs. It has also been suggested as a way to amplify magnetic fields in discs, the instability acting as a nonlinear dynamo. Recent numerical work has shown that a large-scale magnetic field, which is predominantly azimuthal, axisymmetric and has zero net flux, can be sustained...

B. Rafie H. Ghanaati M.A. Oghabian N. RiahicAlam Sh. Mehdipour

Introduction: One of the major causes of image non-uniformity in MRI is due to the existence of  non-homogeneity in RF receive and transmit. This can be the most effective source of error in  quantitative  studies  in  MRI  imaging.  Part  of  this  non-homogeneity  demonstrates  the  characteristics of RF coil and part of it is due to the interaction of RF field with the material being  imaged...

Journal: :caspian journal of internal medicine 0
mehrdad saravi ahmad tamadoni rozita jalalian hasan mahmoodi nesheli mosatafa hojati saeed ramezani

background: iron-mediated cardiomyopathy is the main complication of thalassemia major (tm) patients. therefore, there is an important clinical need in the early diagnosis and risk stratification of patients. the aim of this study was to evaluate the efficacy of tissue doppler imaging (tdi) to study cardiac iron overload in patients with tm using t2* magnetic resonance (mr) as the gold-standard...

Background and Objectives: The use of Magnetic Resonance Imaging (MRI) systems is on the rise and the number of installed systems is constantly increasing all over the world. This raises the possibility for emergency personnel to get in contact with these systems. However, the clothing and working material of paramedics and firefighters is not designed for the use on magnets. M...

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