SAR Temperature Elevations in Pacemaker Holders Exposed to EM Fields Produced by MRI Apparatus

Specific absorption rate (SAR) and temperature distributions, produced inside a thorax model by a magnetic resonance imaging (MRI) apparatus equipped with a birdcage antenna operating at 64 MHz with 100 W of radiated power, have been studied both experimentally and numerically. A pacemaker equipped with a 60-cm long catheter has then been inserted inside the thorax. The presence of this implant gives rise to peak SAR averaged over 1 mm³ of about 1800 W/kg close to the catheter tip, while the average SAR is about 1 W/kg, that is the same value obtained in the absence of the pacemaker. This peak SAR gives rise to temperature increments up to 6 degC for 6 minute MRI investigations. However, lower temperature increments are expected if blood per fusion and thermoregulation are considered