Cataloged from PDF version of article.In this work, it is demonstrated that a dual-drive birdcage coil
can be used to reduce the radiofrequency heating of metallic
devices during magnetic resonance imaging. By controlling the
excitation currents of the two channels of a birdcage coil, the radiofrequency
current that is induced near the lead tip could be
set to zero. To monitor the current, the image artifacts near the
lead tips were measured. The electric field distribution was controlled
using a dual-drive birdcage coil. With this method, the
lead currents and the lead tip temperatures were reduced substantially
[<0.3 C for an applied 4.4 W/kg SAR compared to
>4.9 C using quadrature excitation], as demonstrated by phantom
and animal experiments. The homogeneity of the flip angle
distribution was preserved, as shown by volunteer experiments.
The normalized root-mean-square error of the flip angle distribution
was less than 10% for all excitations. The average specific
absorption rate increased as a trade-off for using different excitation
patterns. Magn Reson Med 69:845–852, 2013. VC 2012
Wiley Periodicals, In
