Elimination of eddy current artifacts in diffusion-weighted echo-planar images: the use of bipolar gradients.

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.