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Radio frequency magnetic field mapping of a 3 Tesla birdcage coil: Experimental and theoretical dependence on sample properties
Author(s) -
Alecci Marcello,
Collins Christopher M.,
Smith Michael B.,
Jezzard Peter
Publication year - 2001
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.1201
Subject(s) - transverse plane , physics , electromagnetic coil , nuclear magnetic resonance , radiofrequency coil , magnetic field , radio frequency , head (geology) , optics , materials science , computational physics , atomic physics , anatomy , medicine , quantum mechanics , geomorphology , geology , telecommunications , computer science
The RF B 1 distribution was studied, theoretically and experimentally, in phantoms and in the head of volunteers using a 3 T MRI system equipped with a birdcage coil. Agreement between numerical simulation and experiment demonstrates that B 1 distortion at high field can be explained with 3D full‐Maxwell calculations. It was found that the B 1 distribution in the transverse plane is strongly dependent on the dielectric properties of the sample. We show that this is a consequence of RF penetration effects combined with RF standing wave effects. In contrast, along the birdcage coil z‐axis the B 1 distribution is determined mainly by the coil geometry. In the transverse plane, the region of B 1 uniformity (within 10% of the maximum) was 15 cm with oil, 6 cm with distilled water, 11 cm with saline, and 10 cm in the head. Along z the B 1 uniformity was 9 cm with phantoms and 7 cm in the head. Magn Reson Med 46:379–385, 2001. © 2001 Wiley‐Liss, Inc.