Parallel transmit pulse design for patients with deep brain stimulation implants

Parallel transmit pulse design for patients with deep brain stimulation implants

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 stimulat...

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Bibliographic Details
Main Authors: Guerin, Bastien, Akgun, Can, Martin, Adrian, Torrado-Carvajal, Angel, Malpica, Norberto, Hernandez-Tamames, Juan A., Schiavi, Emanuele, Eryaman, Yigitcan, Lopez Herraiz, Joaquin, Adalsteinsson, Elfar, Wald, Lawrence
Other Authors: Institute for Medical Engineering and Science
Format: Article
Language:en_US
Published: Wiley Blackwell 2017
Online Access:http://hdl.handle.net/1721.1/110737
https://orcid.org/0000-0001-7208-8863
https://orcid.org/0000-0002-7637-2914
Description
Summary: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.

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