Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada.
Magn Reson Imaging. 2013 Apr;31(3):329-35. doi: 10.1016/j.mri.2012.07.003. Epub 2012 Aug 22.
The corticospinal tract (CST) appears hyperintense on both T2-weighted images and myelin water maps. Here, an extended multiecho T2 relaxation sequence with echoes out to 1120 ms was used to characterize the longer T2 times present in the CST. The T2 distribution from the CST was compared to other white matter structures in 14 healthy subjects. The intra-/extracellular T2 peak of the CST was broadened relative to other white matter structures and often split into two distinct peaks. In the CST, it appeared that the intracellular and extracellular water environments had unique T2 times, causing the intracellular water peak to be pushed down into the myelin water T2 regime and the extracellular peak to be pushed up to longer T2 times. The conventional myelin water T2 limits of 5-40 ms resulted in an artificial increase in myelin water fraction (MWF), causing the CST to be bright on myelin water images. When the upper limit for MWF was decreased to 25 ms, the CST regions exhibited MWF values similar to those found for adjacent anterior and posterior regions. The CST has unique magnetic resonance characteristics, which should be taken into consideration when being examined, especially when compared to pathological tissue.
皮质脊髓束（CST）在 T2 加权图像和髓鞘水图上均表现为高信号。在这里，使用了扩展的多回波 T2 弛豫序列，回波可达 1120ms，以描绘 CST 中存在的较长 T2 时间。在 14 名健康受试者中，将 CST 的 T2 分布与其他白质结构进行了比较。CST 的细胞内/细胞外 T2 峰相对于其他白质结构变宽，并且常常分裂成两个不同的峰。在 CST 中，似乎细胞内和细胞外水环境具有独特的 T2 时间，导致细胞内水峰被推到髓鞘水 T2 范围内，而细胞外峰被推到更长的 T2 时间。传统的髓鞘水 T2 限值为 5-40ms，导致髓鞘水分数（MWF）的人为增加，从而使 CST 在髓鞘水图像上呈现亮信号。当将 MWF 的上限降低到 25ms 时，CST 区域的 MWF 值与相邻的前区和后区相似。CST 具有独特的磁共振特征，在进行检查时应予以考虑，尤其是与病变组织进行比较时。
