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Numerical study of RF exposure and the resulting temperature rise in the foetus during a magnetic resonance procedure

Authors :
Jo Hajnal
Jeffrey Hand
Yuanwei Li
Source :
Physics in Medicine and Biology. 55:913-930
Publication Year :
2010
Publisher :
IOP Publishing, 2010.

Abstract

Numerical simulations of specific absorption rate (SAR) and temperature changes in a 26-week pregnant woman model within typical birdcage body coils as used in 1.5 T and 3 T MRI scanners are described. Spatial distributions of SAR and the resulting spatial and temporal changes in temperature are determined using a finite difference time domain method and a finite difference bio-heat transfer solver that accounts for discrete vessels. Heat transfer from foetus to placenta via the umbilical vein and arteries as well as that across the foetal skin/amniotic fluid/uterine wall boundaries is modelled. Results suggest that for procedures compliant with IEC normal mode conditions (maternal whole-body averaged SAR(MWB)or = 2 W kg(-1) (continuous or time-averaged over 6 min)), whole foetal SAR, local foetal SAR(10 g) and average foetal temperature are within international safety limits. For continuous RF exposure at SAR(MWB) = 2 W kg(-1) over periods of 7.5 min or longer, a maximum local foetal temperature38 degrees C may occur. However, assessment of the risk posed by such maximum temperatures predicted in a static model is difficult because of frequent foetal movement. Results also confirm that when SAR(MWB) = 2 W kg(-1), some local SAR(10g) values in the mother's trunk and extremities exceed recommended limits.

Details

ISSN :
13616560 and 00319155
Volume :
55
Database :
OpenAIRE
Journal :
Physics in Medicine and Biology
Accession number :
edsair.doi.dedup.....01ef37e9b864344f2a2f71a9d3e22d93
Full Text :
https://doi.org/10.1088/0031-9155/55/4/001