Reduction of eddy‐current‐induced distortion in diffusion MRI using a twice‐refocused spin echo

TLDR

Diffusion‑weighted MR images suffer from eddy‑current‑induced distortion, yet they are valuable for diagnosing acute stroke and mapping tissue structure. The study aims to improve the spin‑echo diffusion sequence to reduce distortion and enhance image quality. The authors introduce a twice‑refocused spin‑echo sequence that, by timing a second refocusing pulse and adjusting diffusion gradient timing, nulls or greatly reduces eddy currents without sacrificing scan time. Phantom and human brain experiments show the new sequence yields reduced distortion and clearer diffusion anisotropy images. Published in Magn Reson Med 49:177–182 (2003); © 2003 Wiley‑Liss, Inc.

Abstract

Abstract Image distortion due to field gradient eddy currents can create image artifacts in diffusion‐weighted MR images. These images, acquired by measuring the attenuation of NMR signal due to directionally dependent diffusion, have recently been shown to be useful in the diagnosis and assessment of acute stroke and in mapping of tissue structure. This work presents an improvement on the spin‐echo (SE) diffusion sequence that displays less distortion and consequently improves image quality. Adding a second refocusing pulse provides better image quality with less distortion at no cost in scanning efficiency or effectiveness, and allows more flexible diffusion gradient timing. By adjusting the timing of the diffusion gradients, eddy currents with a single exponential decay constant can be nulled, and eddy currents with similar decay constants can be greatly reduced. This new sequence is demonstrated in phantom measurements and in diffusion anisotropy images of normal human brain. Magn Reson Med 49:177–182, 2003. © 2003 Wiley‐Liss, Inc.