Evaluation of eddy current effects on ultrafast MR imaging

Ultrafast (UF) MR imaging methods acquire all the data for an image reconstruction within several tens of milliseconds. Therefore, various new clinical applications are possible. However, these methods require the rapid switching of extremely large magnetic field gradients that induce eddy currents in the surround electrical conductors. These currents severely degrade the temporal and spatial characteristics of the field gradients, which leads to a bad image quality of the UF MR imaging. So far, this problem has not been sufficiently evaluated quantitatively. Complete temporal compensation for the eddy currents is unattainable because of the output current limitation of the UF MR imaging gradient amplifier system. The authors have evaluated the UF MR image degradation under such imperfect compensation, using computer simulation and experiments