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Exploring the limits of RF shimming for high‐field MRI of the human head
Author(s) -
Mao Weihua,
Smith Michael B.,
Collins Christopher M.
Publication year - 2006
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.21013
Subject(s) - shim (computing) , radio frequency , human head , radiofrequency coil , electromagnetic coil , magnetic field , nuclear magnetic resonance , physics , head (geology) , acoustics , computer science , telecommunications , medicine , quantum mechanics , geomorphology , erectile dysfunction , absorption (acoustics) , geology
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 to create uniform RF magnetic (B 1 ) fields has been called RF shimming, and has certain limits at every frequency as dictated by possible solutions to Maxwell's equations. Here we use numerical calculations to explore the limits of RF shimming in the human head. We found that a 16‐element array can effectively shim a single slice at frequencies up to 600 MHz and the whole brain at up to 300 MHz, while an 80‐element array can shim the whole brain at up to 600 MHz. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.