Non-invasive and time-resolved visualization of the cerebral vasculature by superselective arterial spin labeling

脑血管系统的详细可视化对脑血管疾病的诊断和治疗至关重要。在这些疾病中，对单个血管形态和血流动力学的准确了解影响诊断、治疗计划和治疗监测。目前评估整个脑血管形态和功能的金标准是数字减影血管造影（DSA）。由于该技术具有高度侵入性，因此存在严重并发症的风险，例如由于栓塞事件导致的血管剥离或血管闭塞。此外，DSA以及其他现有的血管造影技术，如计算机断层血管造影（CTA）或磁共振成像（MRI）依赖于电离辐射和/或外源性造影剂，只有DSA可以提供血管选择性测量。动脉自旋标记（ASL）是一种基于MRI的技术，它使用磁性标记的血液作为内源性示踪剂。这是唯一一种完全非侵入性的方法，它提供了将血液标记限制在单个动脉上的可能性，因此，可以分离每条血管对大脑血液供应的贡献。最初是为灌注成像而开发的，目前的方法是使用ASL激发结合适当的读出来显示动脉。ASL有潜力克服其他血管造影方法的局限性，并可能促进血管选择性和时间分辨测量在脑血管系统中的结合。本提案的目的是开发基于ASL的时间分辨，血管选择性血管造影序列，可以添加到当前的临床方案中。首先，我们的目标是这些方法的高质量和可重复性；其次，我们关注这些方法在临床常规中的适用性和可行性，使这些方法在临床诊断和治疗计划中易于使用。我们的课题组在ASL领域及其在多种脑血管疾病中的应用方面有着丰富的经验。新方法将在超选择伪连续ASL （pCASL）的基础上发展，pCASL是一种能够选择性地标记从主要脑供血动脉到供应不同大小脑区域的较小颅内血管的各种大小血管的技术。同时，新技术将在患有脑血管疾病的患者中进行评估，如动静脉畸形、锁骨下偷窃综合征和脑主要供血血管假性闭塞。为了达到最好的效果，我们建议物理学家和医生密切合作。因此，项目的两个方面都得到了关注；开发、实施和改进序列的技术专长，以及测试序列并指出使序列适合临床医生工具的重要方面的医学专长。

A detailed visualization of the cerebral vasculature is crucial for diagnosis and treatment of cerebrovascular diseases. In these, exact knowledge of morphology of individual vessels and resulting hemodynamics effects diagnoses, therapy planning and treatment monitoring.The current gold standard for assessing morphology and function of the entire cerebral vasculature is digital subtraction angiography (DSA). Since this technique is highly invasive, it bears the risk of severe complications such as the dissection of a vessel or vascular occlusion due to embolic events. In addition, DSA as well as other present angiographical techniques such as computed tomographical angiography (CTA) or magnetic resonance imaging (MRI) rely on ionizing radiation and/or exogenous contrast agents and only DSA can provide vessel-selective measurements.Arterial Spin Labeling (ASL) is an MRI based technique that uses magnetically labeled blood as an endogenous tracer. It is the only method that is completely non-invasive and that offers the possibility to restrict the labeling of the blood to an individual artery, hence, to separate the contribution of each vessel to the blood supply of the brain. Originally developed for perfusion imaging, current approaches visualize arteries using ASL excitation in conjunction with appropriate read-out. ASL has the potential to overcome limitations of other angiographic approaches and may facilitate the combination of vessel-selective and time-resolved measurements in the cerebral vasculature. The objective of this proposal is to develop time-resolved, vessel-selective angiography sequences based on ASL that can be added to current clinical protocols. Firstly, we aim for high quality and reproducibility of these methods; secondly, we focus our attention on the applicability and feasibility in clinical routine to make these methods readily available tools in clinical diagnosis and treatment planning.Our research group has broad experience in the field of ASL and its application to a variety of categories of cerebrovascular disease. The new method shall be developed on the basis of superselective pseudo-continuous ASL (pCASL), a technique which is able to selectively label various sized vessels from the major brain feeding arteries down to smaller intracranial vessels supplying brain territories of various sizes.In parallel, the new techniques will be evaluated in patients that suffer from cerebrovascular diseases such as arteriovenous malformation, subclavian steal syndrome, and pseudo-occlusion in major brain feeding vessels. To achieve best results, we propose a close cooperation of a physicist and a physician. Thus, both sides of the project are kept in focus; the technical expertise for developing, implementing, and improving the sequences and the medical expertise to test the sequences and point out the important aspects to make the sequences suitable tools for clinicians.