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RF heating due to conductive wires during MRI depends on the phase distribution of the transmit field
Author(s) -
Yeung Christopher J.,
Susil Robert C.,
Atalar Ergin
Publication year - 2002
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.10310
Subject(s) - electromagnetic coil , phase (matter) , electrical conductor , radio frequency , materials science , field (mathematics) , nuclear magnetic resonance , magnetic field , dielectric heating , radiofrequency coil , electric field , acoustics , mechanics , computational physics , optoelectronics , physics , electrical engineering , composite material , engineering , mathematics , dielectric , quantum mechanics , pure mathematics
In many studies concerning wire heating during MR imaging, a “resonant wire length” that maximizes RF heating is determined. This may lead to the nonintuitive conclusion that adding more wire, so as to avoid this resonant length, will actually improve heating safety. Through a theoretical analysis using the method of moments, we show that this behavior depends on the phase distribution of the RF transmit field. If the RF transmit field has linear phase, with slope equal to the real part of the wavenumber in the tissue, long wires always heat more than short wires. In order to characterize the intrinsic safety of a device without reference to a specific body coil design, this maximum‐tip heating phase distribution must be considered. Finally, adjusting the phase distribution of the electric field generated by an RF transmit coil may lead to an “implant‐friendly” coil design. Magn Reson Med 48:1096–1098, 2002. © 2002 Wiley‐Liss, Inc.