Parallel transmit pulse design for patients with deep brain stimulation implants

Yigitcan Eryaman, Bastien Guerin, Can Akgun, Joaquin L. Herraiz, Adrian Martin, Angel Torrado-Carvajal, Norberto Malpica, Juan A. Hernandez-Tamames, Emanuele Schiavi, Elfar Adalsteinsson, Lawrence L. Wald

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

Purpose Specific absorption rate (SAR) amplification around active implantable medical devices during diagnostic MRI procedures poses a potential risk for patient safety. In this study, we present a parallel transmit (pTx) strategy that can be used to safely scan patients with deep brain stimulation (DBS) implants. Methods We performed electromagnetic simulations at 3T using a uniform phantom and a multitissue realistic head model with a generic DBS implant. Our strategy is based on using implant-friendly modes, which are defined as the modes of an array that reduce the local SAR around the DBS lead tip. These modes are used in a spokes pulse design algorithm in order to produce highly uniform magnitude least-squares flip angle excitations. Results Local SAR (1 g) at the lead tip is reduced below 0.1 W/kg compared with 31.2 W/kg, which is obtained by a simple quadrature birdcage excitation without any sort of SAR mitigation. For the multitissue realistic head model, peak 10 g local SAR and global SAR are obtained as 4.52 W/kg and 0.48 W/kg, respectively. A uniform axial flip angle is also obtained (NRMSE <3%). Conclusion Parallel transmit arrays can be used to generate implant-friendly modes and to reduce SAR around DBS implants while constraining peak local SAR and global SAR and maximizing flip angle homogeneity. Magn Reson Med 73:1896-1903, 2015.

Original languageEnglish (US)
Pages (from-to)1896-1903
Number of pages8
JournalMagnetic resonance in medicine
Volume73
Issue number5
DOIs
StatePublished - May 1 2015

Keywords

  • deep brain stimulation (DBS)
  • electric field steering
  • excitation fidelity
  • global SAR
  • implant safety
  • local SAR
  • parallel transmit (pTx)

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