Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
Magn Reson Med. 2013 Mar 1;69(3):832-8. doi: 10.1002/mrm.24302. Epub 2012 May 3.
Velocity-selective (VS) arterial spin labeling is a promising method for measuring perfusion in areas of slow or collateral flow by eliminating the bolus arrival delay associated with other spin labeling techniques. However, B(0) and B(1) inhomogeneities and eddy currents during the VS preparation hinder accurate quantification of perfusion with VS arterial spin labeling. In this study, it is demonstrated through simulations and experiments in healthy volunteers that eddy currents cause erroneous tagging of static tissue. Consequently, mean gray matter perfusion is overestimated by up to a factor of 2, depending on the VS preparation used. A novel eight-segment B(1) insensitive rotation VS preparation is proposed to reduce eddy current effects while maintaining the B(0) and B(1) insensitivity of previous preparations. Compared to two previous VS preparations, the eight-segment B(1) insensitive rotation is the most robust to eddy currents and should improve the quality and reliability of VS arterial spin labeling measurements in future studies.
速度选择（VS）动脉自旋标记是一种很有前途的方法，可通过消除与其他自旋标记技术相关的团注到达延迟来测量慢血流或侧支血流区域的灌注。然而，VS 准备过程中的 B0 和 B1 不均匀性和涡流会阻碍 VS 动脉自旋标记对灌注的准确定量。在这项研究中，通过在健康志愿者中的模拟和实验证明，涡流会导致静态组织的错误标记。因此，根据使用的 VS 准备方法，平均灰质灌注会被高估高达 2 倍。提出了一种新的八段 B1 不敏感旋转 VS 准备方法，以在保持先前准备的 B0 和 B1 不变的情况下减少涡流效应。与之前的两种 VS 准备方法相比，八段 B1 不敏感旋转对涡流的影响最不敏感，应该会提高未来研究中 VS 动脉自旋标记测量的质量和可靠性。
