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

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.