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. 2011 May;33(5):1209-17.
doi: 10.1002/jmri.22544.

Local specific absorption rate in high-pass birdcage and transverse electromagnetic body coils for multiple human body models in clinical landmark positions at 3T

Desmond T B Yeo  1 , Zhangwei Wang, Wolfgang Loew, Mika W Vogel, Ileana Hancu
Affiliations

Local specific absorption rate in high-pass birdcage and transverse electromagnetic body coils for multiple human body models in clinical landmark positions at 3T

Desmond T B Yeo et al. J Magn Reson Imaging. 2011 May.

Abstract

Purpose: To use electromagnetic (EM) simulations to study the effects of body type, landmark position, and radiofrequency (RF) body coil type on peak local specific absorption rate (SAR) in 3T magnetic resonance imaging (MRI).

Materials and methods: Numerically computed peak local SAR for four human body models (HBMs) in three landmark positions (head, heart, pelvic) were compared for a high-pass birdcage and a transverse electromagnetic 3T body coil. Local SAR values were normalized to the IEC whole-body average SAR limit of 2.0 W/kg for normal scan mode.

Results: Local SAR distributions were highly variable. Consistent with previous reports, the peak local SAR values generally occurred in the neck-shoulder area, near rungs, or between tissues of greatly differing electrical properties. The HBM type significantly influenced the peak local SAR, with stockier HBMs, extending extremities towards rungs, displaying the highest SAR. There was also a trend for higher peak SAR in the head-centric and heart-centric positions. The impact of the coil types studied was not statistically significant.

Conclusion: The large variability in peak local SAR indicates the need to include more than one HBM or landmark position when evaluating safety of body coils. It is recommended that an HBM with arms near the rungs be included to create physically realizable high-SAR scenarios.

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Figures

Fig. 1
Fig. 1
|B1+| of axial slices in unloaded high-pass birdcage (left) and TEM (right) RF body coils (normalized such that peak |B1+|=7.1 μT in the middle of the coils).
Fig. 2
Fig. 2
Axial (top) and coronal (bottom) slices showing peak SAR10g locations for HBMs in HPBC body coil at the head-centered landmark position.
Fig. 3
Fig. 3
Axial (top) and coronal (bottom) slices showing peak SAR10g locations for HBMs in TEM body coil at the head-centered landmark position.
Fig. 4
Fig. 4
Axial (top) and coronal (bottom) slices showing peak SAR10g for HBMs in HPBC coil at heart-centered landmark position.
Fig. 5
Fig. 5
Axial (top) and coronal (bottom) slices showing peak SAR10g for HBMs in TEM coil at heart-centered landmark position.
Fig. 6
Fig. 6
Axial (top) and coronal (bottom) slices showing maximum SAR10g for HBMs in HPBC coil at pelvic-centered landmark position.
Fig. 7
Fig. 7
Axial (top) and coronal (bottom) slices showing maximum SAR10g for HBMs in TEM coil at pelvic-centered landmark position.
Fig. 8
Fig. 8
Box plots showing spread of peak SAR10g values for different (a) body coils, (b) human body models, and, (c) landmark positions. The dots denote the mean SAR10g values of the respective datasets.
See this image and copyright information in PMC

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