Z-gradient coil optimisation in presence of time-varying eddy currents
Synopsis: The switching of magnetic field gradient coils in MRI inevitably induces transient eddy currents in conducting system components such as the cryostat vessel [1]. These eddy currents generate secondary magnetic fields that degrade the spatial and temporal performance of the gradient coil. This theoretical study shows that by incorporating the eddy current effects into the coil optimisation process, it is possible to modify a gradient coil design so that the fields created by the coil and the eddy currents combine together to generate a spatially homogeneous gradient, which follows the desired temporal variation. Shielded and unshielded longitudinal gradient coils are used to exemplify this novel approach.