Thermal simulations in the human head for high field MRI using parallel transmission

Purpose: To investigate, via numerical simulations, the compliance of the specific absorption rate (SAR) versus temperature guidelines for the human head in magnetic resonance imaging procedures utilizing parallel transmission at high field. Materials and Methods: A combination of finite element and...

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Bibliographic Details
Published in:Journal of magnetic resonance imaging 2012-06, Vol.35 (6), p.1312-1321
Main Authors: Massire, Aurélien, Cloos, Martjin A., Luong, Michel, Amadon, Alexis, Vignaud, Alexandre, Wiggins, Christopher J., Boulant, Nicolas
Format: Article
Language:English
Subjects:
Body Temperature - physiology
Body Temperature - radiation effects
Computer Simulation
Dose-Response Relationship, Radiation
Head - physiology
Head - radiation effects
Humans
Magnetic Fields
Magnetic Resonance Imaging
Models, Biological
parallel transmission
Radiation Dosage
safety
SAR
simulation
temperature
Transmit SENSE
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Summary:Purpose: To investigate, via numerical simulations, the compliance of the specific absorption rate (SAR) versus temperature guidelines for the human head in magnetic resonance imaging procedures utilizing parallel transmission at high field. Materials and Methods: A combination of finite element and finite‐difference time‐domain methods was used to calculate the evolution of the temperature distribution in the human head for a large number of parallel transmission scenarios. The computations were performed on a new model containing 20 anatomical structures. Results: Among all the radiofrequency field exposure schemes simulated, the recommended 39°C maximum local temperature was never exceeded when the local 10‐g average SAR threshold was reached. On the other hand, the maximum temperature barely complied with its guideline when the global SAR reached 3.2 W/kg. The maximal temperature in the eye could very well rise by more than 1°C in both cases. Conclusion: Considering parallel transmission, the recommended values of local 10‐g SAR may remain a relevant metric to ensure that the local temperature inside the human head never exceeds 39°C, although it can lead to rises larger than 1°C in the eye. Monitoring temperature instead of SAR can provide increased flexibility in pulse design for parallel transmission. J. Magn. Reson. Imaging 2012;35:1312–1321. © 2012 Wiley Periodicals, Inc.
ISSN:1053-1807
1522-2586
DOI:10.1002/jmri.23542