Novel Ultrashort Echo Time Sequences for Brain MRI

 描述（由申请人提供）：髓磷脂作为轴突周围磷脂膜的绝缘层，在整个大脑的神经元信号传导中起关键作用。髓磷脂的形成在出生后不久就开始了，一直持续到人类生命的第50个十年， 并且是远程神经网络的基础。髓鞘形成的程度及其结构也是许多神经系统疾病的关键特征，特别是脱髓鞘疾病，如多发性硬化症、脑白质营养不良和神经变性。在这个项目中，我们建议开发一种新的MRI方法，用于髓磷脂的非侵入性成像。它是基于一个以前未探索的来源，髓鞘对比，已被证明在最近的体外研究是源于质子在髓鞘磷脂膜。这种对比度的来源没有被任何当前的MRI方法用于髓磷脂成像，因为它具有快速的衰减率（超短T2），这意味着它的信号在使用传统方法获取数据时已经衰减。我们将使用基于超短回波时间（UTE）MRI的方法，这些方法利用专门的激发、采集和重建来检测这种快速衰减的成分。虽然用于成像髓磷脂的当前MRI方法（包括磁化传递、扩散和髓磷脂水部分）依赖于来自水中质子的信号的检测， 这种新的造影剂来源直接来自髓鞘磷脂膜中的质子。我们相信这可以提供更特异的髓鞘成像，从而可以提供髓鞘形成，脱髓鞘，髓鞘形成障碍和髓鞘再生的更特异的成像生物标志物。作为一种更特异的生物标志物，对这种膜成分进行成像可以提高我们对大脑发育的理解，并可用于许多疾病的诊断，定位，手术计划和监测治疗反应。由于这种对比度的来源在很大程度上尚未被探索，我们首先建议在人体研究中描述其MRI特性，包括不同年龄的健康志愿者以及先前发现脱髓鞘病变的多发性硬化症患者。这将提供一个初步的评价，这在很大程度上是未开发的对比度在正常出现灰色和白色物质，以及在脱髓鞘病变的来源。由于这些完整的表征研究需要较长的扫描时间，我们还将开发基于UTE MRI的SNR和对比度有效成像方法，以便在未来的临床评价研究中广泛测量这种对比度来源。

 DESCRIPTION (provided by applicant): Myelin plays a critical role in neuronal signal conduction across the brain as an insulating layer of phospholipid membranes around axons. Myelin formation begins shortly after birth, continuing well into the 5th decade of life in humans, and is the basis for long range neural networks. The degree of myelination and its structure is also a key feature of many neurological disorders, especially demyelinating diseases such as multiple sclerosis, leukodystrophies, and neruodegeneration. In this project, we propose to develop a new MRI method for non-invasive imaging of myelin. It is based on a previously unexplored source of myelin contrast that has been shown in recent ex vivo studies to be originating from protons in the myelin phospholipid membranes. This source of contrast is not exploited by any current MRI methods for imaging myelin because it has a rapid decay rate (ultrashort-T2), meaning its signal has decayed by the time data is acquired using conventional approaches. We will use methods based on ultra- short echo time (UTE) MRI that leverage specialized excitations, acquisitions, and reconstructions in order to detect such rapidly decaying components. While current MRI methods for imaging myelin, including magnetization transfer, diffusion, and myelin water fractions, rely on detection of signal from protons in water, this new source of contrast comes directly from protons in the myelin phospholipid membranes. We believe that this could provide more specific imaging of myelin and thus could provide a more specific imaging biomarker of myelination, demyelination, dysmyelination, and remyelination. As a more specific biomarker, imaging this membrane component could improving our understanding of brain development as well as be applied for diagnosis, localization, surgical planning, and monitoring response to treatment in many disorders. As this source of contrast is largely unexplored, we first propose to characterize its MRI properties in human studies, both in healthy volunteers of various ages as well as multiple sclerosis patients with previously identified demyelinating lesions. This will provide an initial evaluation of this largely unexplored source of contrast in normal appearing gray and white matter as well as in demyelinated lesions. Since these complete characterization studies will require long scan times, we will also develop SNR and contrast efficient imaging methods based on UTE MRI in order to enable widespread measurements of this source of contrast in future clinical evaluation studies.