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

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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.