Imaging Collaterals in Acute Stroke (iCAS)

描述(申请人提供)：侧支血流在急性缺血性中风中起着核心作用，良好侧支的存在与成功再通和不成功再通的临床和放射结果指标的改善有关。尽管如此，目前评估侧支充分性的唯一方法是普及且昂贵的数字减影脑血管造影(DSA)。如果侧支可以使用基于断层图像的非侵入性成像方式进行可视化，那么这将是非常有益的，这样早期的治疗决策就可以纳入这一关键信息。目的和方法急性卒中侧支成像(ICAS)研究的总体目标是利用动脉自旋标记(ASL)这一非增强MRI技术识别和量化经侧支循环传递的脑血流量(CBF)，并确定其对缺血病变生长和患者预后的影响。我们将对180名急性卒中患者进行前瞻性的多中心研究，这些患者在4.5-12小时的时间窗内接受大血管闭塞性卒中的成像，这些患者正在考虑接受血管内溶栓治疗。我们将在我们的快速卒中方案中增加两个ASL序列：用于识别侧支的伪连续ASL(PCASL，2.5min)和用于独立于动脉到达延迟测量定量CBF的速度选择性ASL(VS-ASL，2.5min)。在目标1中，我们将论证DSA和PCASL在抵押品评估方面的等价性，并使用VS-ASL确定抵押品与定量CBF之间的关系。然后，在目标2中，我们将确定ASL是否可以用于补充或取代传统的团注造影剂PWI，确定侧支循环评估对缺血性病变生长的预测能力，并通过检查侧支循环、血管重建和患者预后之间的关系，评估如何将侧支循环测量纳入血管内治疗的患者选择算法。意义我们相信，成功实现这些目标将通过验证一种基于MRI的非侵入性方法来评估侧支的存在和它们提供的CBF的数量，从而显著改善急性中风的护理。ICAS将是首次对ASL进行前瞻性的多中心研究，ASL是一种很有前途的新的非对比剂灌注方法，用于急性卒中。特别是，使用VS-ASL在急性卒中的连续时间点获得定量的CBF测量将产生关于这一关键血流动力学参数的宝贵信息。它将提供一个框架，将侧支状态纳入治疗决策，特别是通过回答侧支非常好或非常差的患者是否从再通中受益的问题。这项研究将使人们更好地了解ASL测量在重症脑血管疾病患者中的益处，并增强MRI在急性缺血性中风中已经具有的重要诊断能力。

DESCRIPTION (provided by applicant): Collateral blood flow plays a central role during acute ischemic stroke, and the presence of good collaterals has been linked to improved clinical and radiologi- cal outcome measures both with and without successful recanalization. Despite this, the only method to assess adequacy of collaterals currently is in- vasive and expensive, digital subtraction cerebral angiography (DSA). It would be tremendously beneficial if collaterals could be visualized using a tomo- graphic, non-invasive imaging based modality, so that early treatment deci- sions could incorporate this critical information. AIMS AND METHODS The overall goal of the imaging the Collaterals in Acute Stroke (iCAS) study, is to identify and quantify cerebral blood flow (CBF) delivered via collateral routes using arterial spin labeling (ASL), a non-contrast MRI technique, and to determine its impact on ischemic lesion growth and patient outcome. We will perform a prospective, multi-center study of 180 acute stroke patients imaged in the 4.5-12 hr time window with large vessel occlusive stroke who are under consideration for endovascular thrombolytic therapy. We will add two ASL sequences to our rapid stroke protocol: pseudocontinuous ASL (pcASL, 2.5 min) for identifying collaterals and velocity-selective ASL (VS-ASL, 2.5 min) for measuring quantitative CBF independent of arterial arrival delay. In Aim 1, we will demonstrate equivalence between DSA and pcASL for collateral assessment, and determine the relationship between collateral and quantitative CBF using VS-ASL. Then, in Aim 2, we will determine whether ASL might be used to supplement or replace conventional bolus contrast PWI, determine the predictive ability of collateral assessment upon ischemic lesion growth, and evaluate how to incorporate collateral measurements into patient selection algorithms for endovascular therapy by examining the relationship between collaterals, revascularization, and patient outcome. SIGNIFICANCE We believe successful attainment of these aims will markedly improve acute stroke care by validating a non-invasive MRI-based method to assess both the presence of collaterals and the amount of CBF they deliver. iCAS will be the first prospective, multi-center study of ASL, a promising new non-contrast perfusion method, in acute stroke. In particular, the use of VS-ASL to obtain quantitative CBF measurements at serial timepoints in acute stroke will yield invaluable information on this critica hemodynamic parameter. It will provide a framework for incorporating collateral status into treatment decision-making, specifically by answering the question of whether patients with either very good or very poor collaterals benefit from recanalization. This study will lead to bettr understanding of the benefit of ASL measurements in patients with severe cerebrovascular disease and enhance the already significant diagnostic power of MRI in acute ischemic stroke.