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A specific absorption rate prediction concept for parallel transmission MR
Author(s) -
Graesslin Ingmar,
Homann Hanno,
Biederer Sven,
Börnert Peter,
Nehrke Kay,
Vernickel Peter,
Mens Giel,
Harvey Paul,
Katscher Ulrich
Publication year - 2012
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.24138
Subject(s) - specific absorption rate , parallel communication , computer science , transmission (telecommunications) , amplitude , field (mathematics) , excitation , absorption (acoustics) , limiting , algorithm , computational physics , physics , acoustics , optics , mathematics , telecommunications , mechanical engineering , quantum mechanics , antenna (radio) , pure mathematics , engineering
The specific absorption rate (SAR) is a limiting factor in high‐field MR. SAR estimation is typically performed by numerical simulations using generic human body models. However, SAR concepts for single‐channel radiofrequency transmission cannot be directly applied to multichannel systems. In this study, a novel and comprehensive SAR prediction concept for parallel radiofrequency transmission MRI is presented, based on precalculated magnetic and electric fields obtained from electromagnetic simulations of numerical body models. The application of so‐called Q ‐matrices and further computational optimizations allow for a real‐time estimation of the SAR prior to scanning. This SAR estimation method was fully integrated into an eight‐channel whole body MRI system, and it facilitated the selection of different body models and body positions. Experimental validation of the global SAR in phantoms demonstrated a good qualitative and quantitative agreement with the predictions. An initial in vivo validation showed good qualitative agreement between simulated and measured amplitude of (excitation) radiofrequency field. The feasibility and practicability of this SAR prediction concept was shown paving the way for safe parallel radiofrequency transmission in high‐field MR. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.