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On the SAR and field inhomogeneity of birdcage coils loaded with the human head
Author(s) -
Jin Jianming,
Chen Ji
Publication year - 1997
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910380615
Subject(s) - electromagnetic coil , specific absorption rate , human head , radiofrequency coil , nuclear magnetic resonance , physics , resonator , magnetic field , magnetic resonance imaging , finite element method , electromagnetic field , electric field , homogeneity (statistics) , acoustics , homogeneous , optics , materials science , absorption (acoustics) , computer science , electrical engineering , radiology , engineering , medicine , quantum mechanics , machine learning , antenna (radio) , thermodynamics
Birdcage coils are widely used as a radiofrequency (RF) resonator in magnetic resonance imaging (MRI) because of their capability to Produce a highly homogeneous B 1 field Over a large volume within the coil. When they are employed for high‐frequency MRI, the interaction between the electromagnetic field and the object to be imaged deteriorates the B 1 ‐field homogeneity and increases the specific absorption rate (SAR) in the object. To investigate this problem, a finite‐element method (FEM) is developed to analyze the SAR and the B 1 field in a two‐dimensional (2D) model of a birdcage coil loaded with a 2D model of a human head. The electric field, magnetic field, and SAR distributions are shown, and a comprehensive study is carried out for both linear and quadrature birdcage coils at 64, 128, 171, and 256 MHz. It is that to generate the same value of the B 1 field, the SAR is increased significantly with the frequency, and for the same imaging method the SAR produced by a quadrature coil is significantly lower than that of a linear coil. It is also shown that the B 1 ‐field inhomogeneity is increased significantly with the frequency.