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.