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Neurostimulation systems for deep brain stimulation: In vitro evaluation of magnetic resonance imaging–related heating at 1.5 tesla
Author(s) -
Rezai Ali R.,
Finelli Daniel,
Nyenhuis John A.,
Hrdlicka Greg,
Tkach Jean,
Sharan Ashwini,
Rugieri Paul,
Stypulkowski Paul H.,
Shellock Frank G.
Publication year - 2002
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.10069
Subject(s) - neurostimulation , specific absorption rate , imaging phantom , torso , magnetic resonance imaging , electromagnetic coil , radiofrequency coil , biomedical engineering , nuclear medicine , head (geology) , radio frequency , nuclear magnetic resonance , materials science , medicine , stimulation , computer science , radiology , physics , anatomy , telecommunications , quantum mechanics , geomorphology , geology , antenna (radio)
Purpose To assess magnetic resonance imaging (MRI)‐related heating for a neurostimulation system (Activa® Tremor Control System, Medtronic, Minneapolis, MN) used for chronic deep brain stimulation (DBS). Materials and Methods Different configurations were evaluated for bilateral neurostimulators (Soletra® Model 7426), extensions, and leads to assess worst‐case and clinically relevant positioning scenarios. In vitro testing was performed using a 1.5‐T/64‐MHz MR system and a gel‐filled phantom designed to approximate the head and upper torso of a human subject. MRI was conducted using the transmit/receive body and transmit/receive head radio frequency (RF) coils. Various levels of RF energy were applied with the transmit/receive body (whole‐body averaged specific absorption rate (SAR); range, 0.98–3.90 W/kg) and transmit/receive head (whole‐body averaged SAR; range, 0.07–0.24 W/kg) coils. A fluoroptic thermometry system was used to record temperatures at multiple locations before (1 minute) and during (15 minutes) MRI. Results Using the body RF coil, the highest temperature changes ranged from 2.5°–25.3° C. Using the head RF coil, the highest temperature changes ranged from 2.3°–7.1° C.Thus, these findings indicated that substantial heating occurs under certain conditions, while others produce relatively minor, physiologically inconsequential temperature increases. Conclusion The temperature increases were dependent on the type of RF coil, level of SAR used, and how the lead wires were positioned. Notably, the use of clinically relevant positioning techniques for the neurostimulation system and low SARs commonly used for imaging the brain generated little heating. Based on this information, MR safety guidelines are provided. These observations are restricted to the tested neurostimulation system. J. Magn. Reson. Imaging 2002;15:241–250. © 2002 Wiley‐Liss, Inc.