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Parallel radiofrequency transmission at 3 tesla to improve safety in bilateral implanted wires in a heterogeneous model
Author(s) -
McElcheran Clare E.,
Yang Benson,
Anderson Kevan J.T.,
Golestanirad Laleh,
Graham Simon J.
Publication year - 2017
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.26622
Subject(s) - specific absorption rate , imaging phantom , magnetic resonance imaging , radiofrequency coil , electromagnetic coil , materials science , electrical conductor , transmission (telecommunications) , radio frequency , image quality , biomedical engineering , channel (broadcasting) , nuclear medicine , computer science , physics , radiology , telecommunications , medicine , composite material , image (mathematics) , quantum mechanics , artificial intelligence , antenna (radio)
Purpose Elongated implanted conductors can interact with the radiofrequency (RF) transmission field during MRI, posing safety concerns of excessive heating in patients with deep brain stimulators. A technique using parallel RF transmission (pTx) is evaluated on an anthropomorphic heterogeneous model with bilateral and unilateral curved wires. Methods Amplitude and phase were optimized by simulation to minimize heating surrounding the implanted wires and to minimizeB 1 +inhomogeneity for four‐channel and eight‐channel pTx in a heterogeneous model. MRI experiments were conducted in an equivalent test phantom created from a common digital mesh file. Results In four‐channel pTx, maximum local specific absorption rate (SAR) was reduced in both unilateral and bilateral wires by 47% and 59%, respectively, but with compromisedB 1 +homogeneity. Optimized eight‐channel pTx substantially reduced local SAR compared with birdcage coil RF excitation in both unilateral and bilateral wires (reduction of maximum local SAR of 79% and 87%, respectively).B 1 +inhomogeneity was limited to 17% and 26%, respectively. Experimental validation with four‐channel pTx showed 80% and 92% temperature reduction at the tips of wire 1 and wire 2, respectively. Conclusion This pTx approach yields promising reductions in local SAR at the tips of unilateral and bilateral implanted wires while maintaining image quality in simulation and experiment. Magn Reson Med 78:2408–2415, 2017. © 2017 International Society for Magnetic Resonance in Medicine.