Reduction of eddy‐current‐induced distortion in diffusion MRI using a twice‐refocused spin echo
Tóm tắt
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.
Từ khóa
Tài liệu tham khảo
WedeenVJ ReeseTG TuchDS WeigellMR DouJ‐G WeisskoffRM CheslerD.Mapping fiber orientation spectra in cerebral white matter with Fourier‐transform diffusion MRI. In: Proceedings of the 8th Annual Meeting of ISMRM Denver 2000. p82.
Waugh JS, 1972, Spin echoes and Loschmidt's paradox, J Magn Reson, 6, 317
ReeseTG WeisskoffRM WedeenVJ.Diffusion NMR facilitated by a refocused eddy‐current EPI pulse sequence. In: Proceedings of the 6th Annual Meeting of ISMRM Sydney Australia 1998. p663.
HeidO.Eddy current‐nulled diffusion weighting. In: Proceedings of the 8th Annual Meeting of ISMRM Denver 2000. p799.
RoemerPB EdelsteinWA HickeyJM.Active magnet shielding of gradient coils in NMR imaging. In: Proceedings of the 5th Annual Meeting of SMRM Montreal Canada 1986. p1067.