Pseudo Random Amplitude Modulation of Arterial Spin Labeling

描述(申请人提供)：动脉自旋标记(ASL)在测量脑血流量(CBF)和局部脑血流灌注方面有许多优点。这些测量对于中风、脑缺血、脑肿瘤和痴呆症的研究、诊断和治疗具有重要意义。ASL是非侵入性的，价格低廉，产生的高分辨率图像很容易与作为同一疗程一部分获得的其他解剖和功能磁共振成像(MRI)扫描进行比较。ASL方法包括通过在成像体积近端的平面将流入的动脉旋转倒置来标记它们。计算CBF的一个主要因素是标记的质子从成像面进入标记面的渡越时间。大多数标准的ASL序列都受到不能直接测量传输时间的限制。取而代之的是，他们依赖于一种排除旅行时间影响的方法，即引入多个来源的混乱和限制 信噪比，尤指在白质中。此外，标准的ASL测量无法确定检测到的变化是血流变化的真实反映，还是已知与神经激活和中风有关的运输时间变化的结果。在……里面 在这项提议中，我们描述了一种新的动脉自旋标记方法，它能够直接测量通过时间。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。这是通过根据伪随机序列标记动脉自旋来实现的。用于伪随机幅度调制或PRAM的序列的数学特性允许恢复作为单个集成采集的一部分存在于成像组织中的所有传输时间。这一方法的实施将为宏观和微观层面的脑血流细节提供新的见解。具体目标是：具体目标1a：在西门子3T Trio扫描仪上实现伪随机动脉调制(PRAM)方案。具体目标2：在模体中使用标准自旋标记和ASL技术验证在SA 1中开发的PRAM序列。具体目标3：通过将PRAM结果与标准PASL序列获得的结果进行比较，将验证研究扩展到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.