Development of Arterial Spin Labeling for Clinical Applications

描述(申请人提供)：中风是一种毁灭性的疾病，由大脑缺乏灌注引起，在美国是第三大死亡原因。动脉自旋标记(ASL)是一种基于MRI的非侵入性血流灌注成像方法，不需要辐射和注射，在卒中的诊断和治疗方面具有巨大的潜力。这个项目的总体目标是开发两种新的ASL方法来评估脑血管疾病，主要焦点是中风。第一种是速度选择性ASL(VSASL)，它解决了传统ASL技术在存在侧支和/或慢血流的情况下无法测量脑血流灌注的问题，这是中风患者经常存在的一种情况。在传统的ASL中，射频脉冲在通往大脑的主要动脉中对动脉血液进行磁性标记。在缓慢或侧支流动的情况下，半衰期约为一秒的标签可能会在被输送到靶组织之前消散，并可能给出没有灌注的错误读数。在VSASL中，动脉血液的标记完全基于流速，而不是位置，允许同时在所有位置标记。VSASL是目前唯一的ASL技术，原则上可以在这些条件下提供准确的血流灌注测量。我们将VSASL应用于临床的具体目标是：1)开发用于VSASL的稳健的3D图像采集方法；2)开发独立于方向的VSASL标记方法；以及3)优化VSASL用于检测慢流。这项工作的结果将是一种稳健的ASL方法，用于中风的定量灌注成像。第二种方法是血管来源成像(VSI)，它允许识别向感兴趣组织供应血液的血管来源。VSI是一种新的技术，具有广泛的临床应用潜力，包括评估颈动脉狭窄、卒中风险评估和识别肿瘤血供。VSI还处于发展的早期阶段，我们在这一领域的目标是解决两个基本的技术问题：1)基于伪连续标记优化VSI标记参数；2)开发高效的VSI编码方案，以最大化VSI测量的信噪比，并允许同时对多条动脉进行编码。这项工作的结果将是稳健的方法，不仅可以测量灌注量，还可以测量得出灌注量的血管来源。

DESCRIPTION (provided by applicant): Stroke is a devastating disease that is caused by a lack of perfusion to the brain, and is the third leading cause of death in the US. Arterial spin labeling (ASL) is an MRI based method for noninvasive imaging of perfusion, using no radiation and no injections, and holds tremendous potential for aiding in the diagnosis and management of stroke. The overall objective of this project is to develop two new ASL methods for the evaluation of cerebrovascular diseases, with stroke as the primary focus. The first is Velocity Selective ASL (VSASL), which addresses the inability of conventional ASL techniques to measure cerebral perfusion in the presence of collateral and/or slow flow, a condition that is often present in stroke patients. In conventional ASL, radiofrequency pulses magnetically tag arterial blood in major arteries leading to the brain. Under conditions of slow or collateral flow, the tag, which decays away with a half life of approximately one second, can dissipate before it can be delivered to the target tissue, and can give a false reading of no perfusion. In VSASL, arterial blood is tagged based purely on flow velocity, rather than location, allowing for tagging in all locations simultaneously. VSASL is currently the only ASL technique that can in principle give accurate measures of perfusion under these conditions. Our specific aims related to bringing VSASL into clinical practice are: 1) Development of a robust 3D image acquisition method for VSASL; 2) Development of a direction independent VSASL tagging method; and 3) Optimization of VSASL for the detection of slow flow. The result of this work will be a robust ASL method for quantitative perfusion imaging in stroke. The second method is Vascular Source Imaging (VSI), which allows for the identification of the vascular source that supplies blood to the tissue of interest. VSI is a new technique with a broad range of potential clinical applications including the evaluation of carotid stenosis, risk assessment for stroke, and the identification of tumor blood supplies. VSI is early in it's development, and our aims in this area are to address two basic technical issues: 1) Optimize VSI tagging parameters based on pseudo-continuous labeling; and 2) Develop efficient VSI encoding schemes to maximize the SNR of the VSI measurement and allow for simultaneous encoding of multiple arteries. The result of this work will be robust methods for measuring not only the amount of perfusion, but also the vascular source from which that perfusion was derived.