Michael Stephen Poole1, Hector Sanchez Lopez1,
Stuart Crozier1
1School of Information Technology and
Electrical Engineering, University of Queensland, Brisbane, QLD, Australia
Modelling
gradient-induced eddy currents using eigenmode analysis reveals a set of
non-interacting modes with characteristic exponential decays. These combine
in conventional gradient coils to produce an eddy current that changes its
magnitude and spatial form in time. This causes gradient pre-emphasis
techniques to be ineffective over the whole imaging region. We propose, and
demonstrate by simulation, that the eddy currents can be made more amenable
to pre-emphasis by suppressing all but one mode. At the same time the primary
field must match the field generated by this mode.