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In vitro and in silico assessment of RF ‐induced heating around intracranial aneurysm clips at 7 T esla
Author(s) -
Noureddine Yacine,
Kraff Oliver,
Ladd Mark E.,
Wrede Karsten H.,
Chen Bixia,
Quick Harald H.,
Schaefers Gregor,
Bitz Andreas K.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26650
Subject(s) - clips , electromagnetic coil , radio frequency , magnetic resonance imaging , polarization (electrochemistry) , dielectric heating , nuclear magnetic resonance , materials science , biomedical engineering , computer science , medicine , physics , chemistry , radiology , surgery , optoelectronics , quantum mechanics , dielectric , telecommunications
Purpose To examine radiofrequency‐induced tissue heating around intracranial aneurysm clips during a 7 Tesla (T) head MR examination. Methods Radiofrequency (RF), temperature simulations, and RF measurements were employed to investigate the effects of polarization and clip length on the electric field (E‐field) and temperature. Heating in body models was studied using both a conservative approach and realistic exposure scenarios. Results Worst‐case orientation was found for clips aligned parallel to the E‐field polarization. Absolute tissue temperature remained below International Electrotechnical Commission regulatory limits for 44 of 50 clinical scenarios. No significant effect on heating was determined for clip lengths below 18.8 mm, and worst‐case heating was found for clip length 51.5 mm. The conservative approach led to a maximum permissible E‐field of 72 V/m corresponding toB 1 +of 1.2 µT, and an accepted power of 4.6 W for the considered RF head coil instead of 38.5 W without clip. Conclusion Safe scanning conditions with respect to RF‐induced heating can be applied depending on the information about the clip gained during screening interviews. However, force and torque measurements in the MR system shall be conducted to give a final statement on the MR safety of aneurysm clips at 7T. Magn Reson Med 79:568–581, 2018. © 2017 International Society for Magnetic Resonance in Medicine.