FDTD Analysis of transient eddy currents induced by gradient coil switching in MRI
Trakic A, Wang H, Liu F, Lopez H, Crozier S
The University of Queensland
In Magnetic Resonance Imaging (MRI), pulsing of magnetic field gradients induces time-varying eddy currents in nearby conductors. These secondary fields are a major cause of concern, since they degrade the image quality by causing misregistration and intensity/phase variations in both images and spectra.A robust analysis scheme allows more complete design and optimisation of gradient coil/magnet combinations and provides indicative predictions of the pre-emphasis and B0-shift compensation waveforms required. A recently proposed three-dimensional (3D), low-frequency Finite-Difference Time-Domain (FDTD) method in cylindrical coordinates is employed to analyse temporal eddy currents and manifest effects (e.g. B0-shift) induced by pulsed actively shielded symmetric/asymmetric transverse x-gradient head and whole body z-coils.