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Reduction of implant RF heating through modification of transmit coil electric field
Author(s) -
Eryaman Yigitcan,
Akin Burak,
Atalar Ergin
Publication year - 2011
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.22724
Subject(s) - reduction (mathematics) , electromagnetic coil , radio frequency , radiofrequency coil , materials science , field (mathematics) , nuclear magnetic resonance , electric field , implant , biomedical engineering , optoelectronics , computer science , telecommunications , electrical engineering , physics , medicine , engineering , mathematics , surgery , quantum mechanics , geometry , pure mathematics
In this work, we demonstrate the possibility to modify the electric‐field distribution of a radio frequency (RF) coil to generate electric field‐free zones in the body without significantly altering the transmit sensitivity. Because implant heating is directly related to the electric‐field distribution, implant‐friendly RF transmit coils can be obtained by this approach. We propose a linear birdcage transmit coil with a zero electric‐field plane as an example of such implant‐friendly coils. When the zero electric‐field plane coincides with the implant position, implant heating is reduced, as we demonstrated by the phantom experiments. By feeding RF pulses with identical phases and shapes but different amplitudes to the two orthogonal ports of the coil, the position of the zero electric‐field plane can also be adjusted. Although implant heating is reduced with this method, a linear birdcage coil results in a whole‐volume average specific absorption rate that is twice that of a quadrature birdcage coil. To solve this issue, we propose alternative methods to design implant‐friendly RF coils with optimized electromagnetic fields and reduced whole‐volume average specific absorption rate. With these methods, the transmit field was modified to reduce RF heating of implants and obtain uniform transmit sensitivity . Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.