Improved PWI Methodology in Acute Clinical Stroke

描述（由申请人提供）： 本次新提交的总体目标是在时间上区分高于临床损伤阈值（CBF降低但高于临界弥散ADC阈值）的亚临床少血与低于存活阈值且有出血风险的脑。在这项为期4年的研究中，每年将研究24名在症状发作6-24小时之间出现卒中样症状的连续住院患者。这些患者将显示广泛的血流值和生理状态，以确定灌注对分段ADC测量的时间依赖性，但仍足够稳定，可以进行测试假设所需的CT和MR研究。 本研究的一个重要方面是建立MR团注跟踪作为定量灌注方法。我们将提高灌注加权MRI（PWI）定量标测灌注（特定目标1）的能力，以便在进展中的急性临床卒中（特定目标2）的情况下建立时间弥散和血流阈值。为此，我们将采集从双回波/双激发梯度回波GRE-EPI团注跟踪动脉输入AIF衍生PWI图像衍生的定量脑血流量（CBF）图。我们将检验以下假设：从我们的自动AIF选择去卷积例程测量的CBF值与“金标准”XeCT值（在就诊时从相同患者获得）的相关性优于用户定义的AIF选择。然后，我们将MR灌注（CBF、MTT和CBV）和XeCT CBF值共同配准到这些患者的分段灰色和白色物质扩散（traceADC、11-13特征值和各向异性FA分数）分布上。 在成功完成这些研究后，我们将建立一些高度准确的预测工具，通过提供进展性梗死的局部生理状态的快照，使用MRI评估脑缺血。我们相信，这一信息将导致新的措施，临床管理，并最终允许管理决策，在个别患者的治疗时间窗口，而不是目前的概念，一个刚性的时间窗口。

DESCRIPTION (provided by applicant): The overall goal of this new submission is to temporally differentiate subclinical oligemia above the threshold for clinical impairment (reduced CBF yet above a critical diffusion ADC threshold) from brain below thresholds of viability and at risk for hemorrhage. For each year of this 4-year study, 24 consecutive inpatients presenting with stroke-like symptoms between 6-24 hours of symptom onset will be studied. These patients will display a wide range of blood flow values and physiological states over which to determine the temporal dependences of perfusion on segmented ADC measures, yet be stable enough to undergo both the CT and MR studies needed to test the hypotheses. One important aspect of this study is to establish MR bolus-tracking as a quantitative perfusion method. We will improve the ability of perfusion-weighted MRI (PWI) to quantitatively map perfusion (Specific Aim 1) in order to establish temporal diffusion and flow thresholds in the setting of evolving acute clinical stroke (Specific Aim 2). To do this, we will acquire quantitative cerebral blood flow (CBF) maps derived from dualecho/ dual-shot gradient-echo GRE-EPI bolus tracking arterial input AIF-derived PWI images. We will test the hypothesis that CBF values measured from our automated AIF selection deconvolution routines will better correlate with the "gold standard" XeCT values (acquired from the same patients at presentation) than will user-defined AIF selections. We will then co-register the MR perfusion (CBF, MTT, and CBV) and XeCT CBF values onto segmented gray and white matter diffusion (traceADC, 11-13 eigenvalues, and fractional anisotropy FA) distributions in these patients. Upon successful completion of these studies, we will have established a number of highly accurate predictive tools for evaluating brain ischemia using MRI by providing a snap-shot of the regional physiological status of evolving infarcts. We believe that this information will lead to new measures for clinical management and will eventually allow management decisions to be made within an individual patient's therapeutic time window as opposed to current conceptions of a rigid time window.