Department of Neurology, University of California Los Angeles, Los Angeles, California 90095, USA.
Magn Reson Med. 2012 Jul;68(1):130-9. doi: 10.1002/mrm.23218. Epub 2011 Nov 29.
A new technique is introduced in this study for in vivo measurement of arterial cerebral blood volume by combining arterial spin labeling with a segmented multiphase balanced steady-state free precession (bSSFP) readout sequence. This technique takes advantage of the phenomenon that the longitudinal magnetization of flowing blood is not or only marginally disturbed (besides T(1) relaxation) by the bSSFP ± α pulse train. When the blood water exchanges into tissue, it becomes quickly saturated by the bSSFP pulse train due to 0 velocity and reduced T(1), T(2) relaxation times. Therefore, labeled blood water behaves like an intravascular contrast agent in multiphase bSSFP scans, and can be used to quantify arterial cerebral blood volume in a similar way as dynamic susceptibility contrast MRI. Both Bloch equation simulation and in vivo experiments were carried out to demonstrate the feasibility for quantifying cerebral blood volume in arteries, arterioles, and capillaries using two variants of the proposed method. Functional MRI of visual cortex stimulation was further performed using multiphase bSSFP-based arterial spin labeling and compared with vascular-space occupancy contrast. The proposed multiphase bSSFP-based arterial spin labeling technique may allow separation of cerebral blood volume of different vascular compartments for functional MRI studies and clinical evaluation of the cerebral vasculature.
本研究提出了一种新的技术，通过结合动脉自旋标记与分段多相平衡稳态自由进动（bSSFP）读取序列，用于在体测量动脉脑血容量。该技术利用了以下现象：流动血液的纵向磁化除 T(1)弛豫外，不受 bSSFP ± α 脉冲序列的干扰（除 T(1)弛豫外）。当血液水进入组织时，由于 0 速度和降低的 T(1)、T(2)弛豫时间，它很快被 bSSFP 脉冲序列饱和。因此，标记的血液水在多相 bSSFP 扫描中表现得像血管内对比剂，可以以类似于动态对比 MRI 的方式定量动脉脑血容量。通过 Bloch 方程模拟和体内实验，证明了使用两种所提出方法变体定量动脉、小动脉和毛细血管中脑血容量的可行性。进一步使用基于多相 bSSFP 的动脉自旋标记进行视皮层刺激的功能 MRI，并与血管空间占有率对比进行比较。所提出的基于多相 bSSFP 的动脉自旋标记技术可能允许对不同血管腔室的脑血容量进行分离，用于功能 MRI 研究和对脑血管的临床评估。
