Comparison study of RF-induced heating in leg phantom with circular external fixator for TEM and birdcage coils at 3 T

The objective of this study is to numerically compare the radio frequency (RF)-induced heating in transverse electromagnetic (TEM) coil and birdcage (BC) coil in the presence of circular leg fixator. We show that TEM coil generates a larger peak specific absorption rate averaged over 1 gram (SAR1g) than BC coil in the leg phantom with a generic circular external fixator. In the specific case, the peak SAR1g in TEM coil can be 1.5 times higher than it in BC coil. It is further shown that the larger electric field outside the leg phantom in TEM coil is the root reason why the circular fixation device heats more, particularly around the tip area, than when exposed in BC coil. Moreover, the effects of the strut height and ring frame radius of the generic circular external fixator on the RF-induced heating are also investigated. It is found that enlarging the height of the strut or the radius of the ring frame will increase the heating level for both TEM and BC coils.