Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 71, Issue 2, Pages 839-845Publisher
WILEY-BLACKWELL
DOI: 10.1002/mrm.24690
Keywords
local field enhancement; specific absorption rate; large-scale anatomical property; safety
Funding
- EUREKA [E!4144]
- CTI [9193.1]
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PurposeRadiofrequency energy deposition in magnetic resonance imaging must be limited to prevent excessive heating of the patient. Correlations of radiofrequency absorption with large-scale anatomical features (e.g., height) are investigated in this article. Theory and MethodsThe specific absorption rate (SAR), as the pivotal parameter for quantifying absorbed radiofrequency, increases with the radial dimension of the patient and therefore with the large-scale anatomical properties. The absorbed energy in six human models has been modeled in different Z-positions (head to knees) within a 1.5T bodycoil. ResultsFor a fixed B1+ incident field, the whole-body SAR can be up to 2.5 times higher (local SAR up to seven times) in obese adult models compared to children. If the exposure is normalized to 4 W/kg whole-body SAR, the local SAR can well-exceed the limits for local transmit coils and shows intersubject variations of up to a factor of three. ConclusionsThe correlations between anatomy and induced local SAR are weak for normalized exposure, but strong for a fixed B1+ field, suggesting that anatomical properties could be used for fast SAR predictions. This study demonstrates that a representative virtual human population is indispensable for the investigation of local SAR levels. Magn Reson Med 71:839-845, 2014. (c) 2013 Wiley Periodicals, Inc.
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