Consideration of magnetically‐induced and conservative electric fields within a loaded gradient coil

We present a method to calculate the electric (E)‐fields within and surrounding a human body in a gradient coil, including E‐fields induced by the changing magnetic fields and “conservative” E‐fields originating with the scalar electrical potential in the coil windings. In agreement with previous numerical calculations, it is shown that magnetically‐induced E‐fields within the human body show no real concentration near the surface of the body, where nerve stimulation most often occurs. Both the magnetically‐induced and conservative E‐fields are shown to be considerably stronger just outside the human body than inside it, and under some circumstances the conservative E‐fields just outside the body can be much larger than the magnetically‐induced E‐fields there. The order of gradient winding and the presence of conductive RF shield can greatly affect the conservative E‐field distribution in these cases. Though the E‐fields against the outer surface of the body are not commonly considered, understanding gradient E‐fields may be important for reasons other than peripheral nerve stimulation (PNS), such as potential interaction with electrical equipment. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.