Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, MD, USA.
J Magn Reson. 2012 Aug;221:24-31. doi: 10.1016/j.jmr.2012.04.010. Epub 2012 Apr 28.
In vivo MRI data can be corrupted by motion. Motion artifacts are particularly troublesome in Diffusion Weighted MRI (DWI), since the MR signal attenuation due to Brownian motion can be much less than the signal loss due to dephasing from other types of complex tissue motion, which can significantly degrade the estimation of self-diffusion coefficients, diffusion tensors, etc. This paper describes a snapshot DWI sequence, which utilizes a novel single-sided bipolar diffusion sensitizing gradient pulse within a spin echo sequence. The proposed method shortens the diffusion time by applying a single refocused bipolar diffusion gradient on one side of a refocusing RF pulse, instead of a set of diffusion sensitizing gradients, separated by a refocusing RF pulse, while reducing the impact of magnetic field inhomogeneity by using a spin echo sequence. A novel MRI phantom that can exhibit a range of complex motions was designed to demonstrate the robustness of the proposed DWI sequence.
体内 MRI 数据可能会受到运动的影响。运动伪影在扩散加权 MRI（DWI）中特别麻烦，因为由于布朗运动导致的 MR 信号衰减可能比由于来自其他类型的复杂组织运动的相位失相干导致的信号损失小得多，这会显著降低自扩散系数、扩散张量等的估计。本文描述了一种快照 DWI 序列，该序列在自旋回波序列中利用了一种新颖的单边双极扩散敏感梯度脉冲。所提出的方法通过在重聚焦 RF 脉冲的一侧施加单个重聚焦双极扩散梯度，而不是通过重聚焦 RF 脉冲分离的一组扩散敏感梯度，来缩短扩散时间，同时通过使用自旋回波序列来减少磁场不均匀性的影响。设计了一种新颖的 MRI 仿体，可以展示一系列复杂运动，以证明所提出的 DWI 序列的稳健性。
