Pseudo Random Amplitude Modulation of Arterial Spin Labeling

描述（由申请人提供）：动脉自旋标记（ASL）在测量脑血流量（CBF）和局部脑灌注方面具有许多优势。这种测量对于中风、缺血、脑肿瘤和痴呆的研究和诊断以及治疗是重要的。ASL是非侵入性的，廉价的，并产生高分辨率的图像，很容易与其他解剖和功能磁共振成像（MRI）扫描采集作为同一会话的一部分。ASL方法涉及通过在成像体积近端的平面处反转流入的动脉自旋来标记流入的动脉自旋。计算CBF的一个主要因素是标记质子从成像平面进入标记平面的渡越时间。大多数标准ASL序列都受到不能直接测量渡越时间的限制。相反，他们依赖于一种分解旅行时间影响的方法，这种方法引入了多种混淆和限制来源 信噪比，特别是在白色物质中。此外，标准ASL测量无法确定所检测到的变化是否真实地反映了流量变化或已知涉及神经激活和中风的通过时间改变的结果。在 在这个提议中，我们描述了一种能够直接测量通过时间的动脉自旋标记的新方法。我们的方法提供了标准ASL的优点，同时消除了它的一些限制。这通过根据伪随机序列标记动脉自旋而成为可能。用于伪随机幅度调制或PRAM的序列的数学特性允许恢复成像组织中存在的所有渡越时间作为单个集成采集的一部分。这种方法的实施应提供新的见解，在宏观和微观层面上的脑血流的细节。具体目标1a：在Siemens 3T Trio扫描仪上实现伪随机动脉调制（PRAM）方案。具体目标2：在体模中使用标准自旋标记和ASL技术验证SA 1中开发的PRAM序列。具体目标3：通过比较PRAM结果与标准PASL序列获得的结果，将确认研究扩展至接受视觉刺激的人类志愿者。

DESCRIPTION (provided by applicant): Arterial spin labeling (ASL) has many advantages for the measurement of cerebral blood flow (CBF) and regional brain perfusion. Such measurements are significant for research and diagnosis and treatment of stroke, ischemia, brain tumors, and dementia. ASL is non-invasive, inexpensive, and produces high-resolution images that are easily compared with other anatomical and functional magnetic resonance imaging (MRI) scans acquired as part of the same session. The ASL method involves labeling inflowing arterial spins by inverting them at a plane proximal to the imaging volume. A major factor in the calculation of CBF is the transit time for the labeled protons to pass from the imaging plane and into the labeling plane. Most standard ASL sequences suffer from the limitation that they cannot measure transit times directly. Instead, they rely on a method of factoring out the effect of travel times that is introduces multiple sources of confound and limits signal-to-noise ratio, especially in white matter. Furthermore, standard ASL measurements are unable to determine whether the changes detected are truly reflections of changes in flow or the result of the alterations in transit times known to be involved in neural activation and stroke. In this proposal, we describe a novel method of arterial spin labeling that is able to directly measure transit times. Our method offers the advantages of standard ASL while removing some of its limitations. This is made possible by labeling the arterial spins according to a pseudo random sequence. The mathematical properties of the sequence used for pseudo random amplitude modulation, or PRAM, allow recovery of all the transit times present in the imaged tissue as part of a single integrated acquisition. Implementation of this method should provide novel insights into the details of cerebral blood flow at both the macroscopic and microscopic levels. Detailed specific aims are: Specific Aim 1a: Implement the pseudo random arterial modulation (PRAM) scheme on a Siemens 3T Trio scanner. Specific Aim 2: Validate the PRAM sequence developed in SA 1 using standard spin tagging and ASL techniques in phantoms. Specific Aim 3: Extend the validation studies to human volunteers undergoing visual stimulation by comparing the PRAM results to those acquired by standard PASL sequences.