Verbree Jasper, van Osch Matthias J P
Department of Radiology, C.J. Gorter Center for High Field MRI, Leiden Institute of Brain and Cognition, Leiden University Medical Center, PO-box 9600, 2300 RC, Leiden, The Netherlands.
MAGMA. 2018 Feb;31(1):223-233. doi: 10.1007/s10334-017-0611-6. Epub 2017 Mar 9.
In arterial spin labeling (ASL), the cardiac cycle might adversely influence signal-stability by varying the amount of label created, labeling efficiency and/or transport times. Due to the long labeling duration in pseudo-Continuous ASL (pCASL), the blood labeled last contributes most to the ASLsignal. The present study investigated, using numerical simulations and in vivo experiments, the effect of the cardiac cycle on pCASL, thereby focusing on the end-of-labeling.
In the in vivo experiments the end-of-labeling was timed to a specific cardiac phase while a long labeling duration of >7 s was used to isolate the influence of the lastly labeled spins on ASL-signal stability.
Simulations showed dependence of the ASL-signal on the cardiac phase of the end-of-labeling, and that the variation in signal was more pronounced at lower heart rates. The ASL-signal variation was small (~4%), but could be effectively reduced by simulated end-of-labeling triggering. In vivo, no difference in mean CBF (p = 0.58) nor in CBF temporal-STD (p = 0.44) could be detected between triggered and non-triggered acquisitions.
Influence of the cardiac cycle on pCASL-signal stability is small and triggering the start-of-labeling and end-of-labeling can be considered not to have practical implications to improve stability.
在动脉自旋标记（ASL）中，心动周期可能会通过改变标记物生成量、标记效率和/或传输时间对信号稳定性产生不利影响。由于伪连续ASL（pCASL）的标记持续时间较长，最后标记的血液对ASL信号的贡献最大。本研究通过数值模拟和体内实验，研究了心动周期对pCASL的影响，重点关注标记结束时的情况。
在体内实验中，将标记结束时间设定为特定的心相，同时使用大于7秒的长标记持续时间来分离最后标记的自旋对ASL信号稳定性的影响。
模拟显示ASL信号依赖于标记结束时的心相，并且在较低心率下信号变化更为明显。ASL信号变化较小（约4%），但通过模拟标记结束触发可有效降低。在体内，触发采集和未触发采集之间在平均脑血流量（p = 0.58）和脑血流量时间标准差（p = 0.44）方面均未检测到差异。
心动周期对pCASL信号稳定性的影响较小，标记开始和标记结束触发可被认为对提高稳定性没有实际意义。
