Parallel radiofrequency transmission at 3 tesla to improve safety in bilateral implanted wires in a heterogeneous model

Clare E. McElcheran*, Benson Yang, Kevan J.T. Anderson, Laleh Golestanirad, Simon J. Graham

*Corresponding author for this work

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)2406-2415
Number of pages10
JournalMagnetic resonance in medicine
Volume78
Issue number6
DOIs
StatePublished - Dec 2017

Keywords

  • RF shimming
  • deep brain stimulation
  • optimization
  • parallel RF transmission

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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