Related Experiment Video
Updated: Mar 7, 2026
Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement
Published on: June 25, 2016
Parallel radiofrequency transmission at 3 tesla to improve safety in bilateral implanted wires in a heterogeneous
Clare E McElcheran1,2, Benson Yang1, Kevan J T Anderson1
1Physical Sciences Platform, Sunnybrook Health Sciences Institute, Toronto, Canada.
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 minimize B1+ 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 compromised B1+ 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). B1+ 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.
