Interaction between 3-T MRI systems and patients with an implanted pacemaker

In this paper, a transverse electro-magnetic (TEM) coil operating at 128 MHz in a 3-T magnetic resonance imaging system has been studied in terms of the interaction with patients with or without an implanted pacemaker. The pacemaker 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 either box or anatomical models of the thorax. Electromagnetic and thermal simulations have been performed by using finite difference time domain codes. The obtained results show that in the absence of the pacemaker, and for a radiated power producing in the box a whole body specific absorption rate (SAR) of 1 W/kg, that is a typical value for MRI examinations, the coil produces in the anatomical models peak temperature values lower than the limits issued by the International Electrotechnical Commission (IEC). In the presence of the pacemaker, temperature increments at the catheter tip in excess of those issued by the IEC standard are obtained when the MRI scanned area involves the pacemaker region. The 3-T coil produces lower SAR and temperature increments with respect to a 64-MHz (1.5-T system) birdcage antenna in patients with implanted pacemaker.