Correction of EPI Nyquist ghosting caused by the non-uniform frequency response of the MRI receiver chain
Weiskopf N, Josephs O, Deichmann R
University College London
The acquisition time in rectilinear echo-planar imaging (EPI) is usually minimized by bi-directional scanning in the readout (RO) direction. Differences between the two acquisition directions lead to systematic signal variations between alternate phase-encoding lines and so to Nyquist ghosting. Recently, the MRI receiver frequency response has been shown to contribute a spatially variable ghost, because it leads to different amplitude modulations for the two acquisition directions. Here, we report a method for reducing this type of ghosting and show its effectiveness experimentally.