Paramagnetic shimming for high-field MRI
نویسندگان
چکیده
منابع مشابه
Paramagnetic shimming for high- eld MRI
The diamagnetism of biological tissues reduces the homogeneity of the magnetic field and may limit the number of samples in multi-sample gradient-recalled echo (GRE) experiments. This study aims to 1) evaluate the magnetic field distortions and signal loss artifacts in GRE images of proximal water samples, and 2) develop a passive shimming device to overcome this limitation. The magnetic field ...
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We propose a new passive shimming strategy for variable-field NMR experiments, in which the magnetic field produced by paramagnetic shim pieces placed inside the magnet bore compensates the inhomogeneity of a variable-field magnet for a wide range of magnet currents. Paramagnetic shimming is demonstrated in (7)Li, (87)Rb, and (45)Sc NMR of a liquid solution sample in magnetic fields of 3.4, 4.0...
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Several methods have been proposed for overcoming the effects of radiofrequency (RF) magnetic field inhomogeneity in high-field MRI. Some of these methods rely at least in part on the ability to independently control magnitude and phase of different drives in either one multielement RF coil or in different RF coils in a transmit array. The adjustment of these drive magnitudes and phases alone t...
متن کاملA theoretical approach based on electromagnetic scattering for analysing dielectric shimming in high-field MRI.
PURPOSE In this study, we analyzed dielectric shimming by formulating it as an electromagnetic scattering problem using integral equations. METHODS Three-dimensional simulations of the radiofrequency field in two configurations using different materials were analyzed in terms of induced currents and secondary fields. A two-dimensional integral equation method with different backgrounds was us...
متن کاملA Complementary Images Shimming Method to Mitigate B1 Inhomogeneity for High Field MRI
INTRODUCTION The B1 inhomogeneity is well known to be a source of artifact in high field MRI, and requires the use of multiple-channel parallel transmit coil to reduce the artifact by making either the B1 distribution (static shimming) or the flip angle distribution (dynamic shimming) as uniform as possible [1]. The former method complies with most imaging sequences, albeit limited to a small R...
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ژورنال
عنوان ژورنال: Brazilian Journal of Physics
سال: 2009
ISSN: 0103-9733
DOI: 10.1590/s0103-97332009000300008