Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz.

Details

Serval ID
serval:BIB_15F99DECB011
Type
Article: article from journal or magazin.
Collection
Publications
Title
Temperature and SAR calculations for a human head within volume and surface coils at 64 and 300 MHz.
Journal
Journal of Magnetic Resonance Imaging
Author(s)
Collins C.M., Liu W., Wang J., Gruetter R., Vaughan J.T., Ugurbil K., Smith M.B.
ISSN
1053-1807 (Print)
ISSN-L
1053-1807
Publication state
Published
Issued date
2004
Volume
19
Number
5
Pages
650-656
Language
english
Notes
Publication types: Journal Article ; Research Support, U.S. Gov't, P.H.S.Publication Status: ppublish
Abstract
PURPOSE: To examine relationships between specific energy absorption rate (SAR) and temperature distributions in the human head during radio frequency energy deposition in MRI.
MATERIALS AND METHODS: A multi-tissue numerical model of the head was developed that considered thermal conductivity, heat capacity, perfusion, heat of metabolism, electrical properties, and density. Calculations of SAR and the resulting temperature increase were performed for different coils at different frequencies.
RESULTS: Because of tissue-dependent perfusion rates and thermal conduction, there is not a good overall spatial correlation between SAR and temperature increase. When a volume coil is driven to induce a head average SAR level of either 3.0 or 3.2 W/kg, it is unlikely that a significant temperature increase in the brain will occur due to its high rate of perfusion, although limits on SAR in any 1 g of tissue in the head may be exceeded.
CONCLUSION: Attempts to ensure RF safety in MRI often rely on assumptions about local temperature from local SAR levels. The relationship between local SAR and local temperature is not, however, straightforward. In cases where high SAR levels are required due to pulse sequence demands, calculations of temperature may be preferable to calculations of SAR because of the more direct relationship between temperature and safety.
Keywords
Equipment Safety, Finite Element Analysis, Head/physiology, Humans, Magnetic Resonance Imaging/instrumentation, Models, Biological, Temperature, Thermal Conductivity
Pubmed
Web of science
Create date
04/08/2010 15:28
Last modification date
20/08/2019 12:45
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