Using Shape Optimization to Linearise the Eddy Current Field

Hector Sanchez¹, Michael Poole¹, Stuart Crozier¹

MRI requires rapidly switched magnetic field gradients. This time-dependent magnetic fields induce eddy currents in nearby conducting structures. These currents generate detrimental transient magnetic fields in the region of interest (ROI) and hence current compensation (CC) is required to minimize the consequential image distortion. In order to apply successfully CC techniques, it is required that the primary and the secondary magnetic fields possess a similar spatial form in the ROI. We investigated by simulation, the effect of re-shaping a highly conducting passive shield surrounding a gradient coil (and the gradient coil surface) over the matching field for optimal current compensation.