Alexander A L, Tsuruda J S, Parker D L
Department of Radiology, University of Utah, Salt Lake City, 84132, USA.
Magn Reson Med. 1997 Dec;38(6):1016-21. doi: 10.1002/mrm.1910380623.
Small gradient fields resulting from incompletely canceled eddy currents can cause geometric distortion in echo-planar images. Although this distortion is negligible in most echoplanar applications, the large gradient pulses used in diffusion-weighted echo-planar imaging can result in significant image distortion. In this report, it is shown that this distortion can be significantly reduced by the application of bipolar gradient waveforms. Both bipolar diffusion-sensitizing gradients and an inverted gradient preparatory pulse were examined for minimizing the eddy currents responsible for these distortions.
由未完全抵消的涡流产生的小梯度场会导致回波平面图像中的几何失真。尽管这种失真在大多数回波平面应用中可以忽略不计，但扩散加权回波平面成像中使用的大梯度脉冲会导致显著的图像失真。在本报告中，表明通过应用双极梯度波形可以显著降低这种失真。研究了双极扩散敏感梯度和反向梯度预备脉冲，以最小化导致这些失真的涡流。
