Hennel F
MR Centre, FORENAP, Rouffach, 68250, France.
J Magn Reson. 1998 Oct;134(2):206-13. doi: 10.1006/jmre.1998.1502.
The method to reduce the ghost artifact in echo-planar imaging (EPI) using a phase correction derived from the image data (M. H. Buonocore and L. Gao, Magn. Reson. Med. 38, 89 (1997)) is generalized to multishot (interleaved) EPI, where the artifact takes the form of multiple ghosts. The method is shown to be much more sensitive to noise when applied to standard interleaved data than is the case with single-shot EPI, because the calculation must be based on high-order ghosts of low intensity. A modified interleaving scheme is proposed for multishot EPI in which the initial trajectory direction alternates in consecutive shots and the number of shots is odd. With this scheme, only a single ghost shifted by one-half of the field of view appears just as in the single-shot EPI, and the image-based phase correction can be applied with the usual sensitivity to noise.
利用从图像数据中导出的相位校正来减少回波平面成像（EPI）中鬼伪影的方法（M. H. 布奥诺科尔和L. 高，《磁共振医学》38卷，89页（1997年））被推广到多激发（交错）EPI，在这种情况下，伪影呈现为多个鬼影的形式。结果表明，当应用于标准交错数据时，该方法对噪声的敏感度比单激发EPI的情况要高得多，因为计算必须基于低强度的高阶鬼影。针对多激发EPI提出了一种改进的交错方案，其中初始轨迹方向在连续激发中交替，且激发次数为奇数。采用这种方案时，仅会出现一个偏移了半个视野的单个鬼影，就如同在单激发EPI中一样，并且基于图像的相位校正可以以通常的噪声敏感度来应用。
