IMAGE-BASED REDUCTION OF ARTIFACTS IN MULTISHOT ECHO-PLANAR IMAGING

The method to reduce the ghost artifact in echo-planar imaging (EPI) u sing a phase correction derived from the image data (M. H. Buonocore a nd L. Gao, Magn. Reson. Med. 38, 89 (1997)) is generalized to multisho t (interleaved) EPI, where the artifact takes the form of multiple gho sts. The method is shown to be much more sensitive to noise when appli ed to standard interleaved data than is the case with single-shot EPI, because the calculation must be based on high-order ghosts of low int ensity. A modified interleaving scheme is proposed for multishot EPI i n which the initial trajectory direction alternates in consecutive sho ts and the number of shots is odd. With this scheme, only a single gho st shifted by one-half of the field of view appears just as in the sin gle-shot EPI, and the image-based phase correction can be applied with the usual sensitivity to noise. (C) 1998 Academic Press.