Interaction between MRI RF field and pacemaker holders: A comparison between birdcage and TEM coils in 3 T systems

In this paper Birdcage and TEM coils operating at 128 MHz have been studied and compared in terms of their interaction with pacemaker holders. The pacemaker (PM) has been simulated as a copper box with a catheter constituted by an insulated copper wire with an uncapped tip and it has been placed inside a box model of the thorax. Electromagnetic and thermal simulations have been performed by using CST microwave studio. The obtained results show that in the absence of the PM the two coils produce SAR values lower than the ICNIRP limits while, in the presence of the PM, the birdcage antenna overcomes the ICNIRP limit on the SAR as averaged over 10 g while both coils give rise to temperature increments at the catheter tip in excess of those issued by the ICNIRP standard. In general the TEM coil produces lower SAR and temperature increments with respect to the birdcage antenna.