Numerically‐simulated induced electric field and current density within a human model located close to a z ‐gradient coil

Purpose To simulate exposure (e.g., during interventional procedures) of a worker close to an operating MR scanner by calculating electric fields and current density within an anatomically realistic body model due to a z ‐gradient coil and to compare results with safety guidelines and European Directive 2004/40/EC. Materials and Methods Electric field and current density in an adult male model located at three positions within the range 0.19–0.44 m from the end of a generic z ‐gradient coil were calculated using the time‐domain finite integration technique (FIT). Frequency scaling was used in which quasistatic conditions were assumed and results obtained at 1 MHz (assuming tissue conductivity values at 1 kHz) were scaled to 1 kHz. Results Current density (averaged over 1 cm 2 ) in central nervous system (CNS) tissues up to 20.6 mA m −2 and electric fields (averaged over 5 mm) up to 4.1 V m −1 were predicted for a gradient of 10 mT m −1 and slew rate of 10 T m −1 second −1 . Conclusion Compliance with 2004/40/EC, and with basic restriction values of Institute of Electrical and Electronics Engineers (IEEE) C95.6‐2002, was predicted only at impracticably low gradients/slew rates in the ranges 4.9–9.1 mT m −1 /4.9–9.1 T m −1 second −1 and 5–21 mT m −1 /5–21 T m −1 second −1 , respectively. J. Magn. Reson. Imaging 2007;26:1286–1295. © 2007 Wiley‐Liss, Inc.