Rapid Real-Time MR Angiography of Suspected Stroke

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Project Summary/Abstract: The objective of this project is to develop and validate very rapid and robust next-generation magnetic resonance (MR) protocols for anatomic and hemodynamic evaluation of the head and neck vessels in patients with suspected stroke. Emergent diagnostic imaging evaluation of suspected stroke typically involves a non- contrast CT to detect intracranial hemorrhage. However, subsequent patient management is based on the much more extensive anatomical and functional information provided by magnetic resonance imaging (MRI). The MRI protocol typically consists of anatomic imaging, diffusion-weighted imaging, MR angiography (MRA) to detect stenosis and occlusion in the neurovascular system, and contrast-enhanced perfusion imaging. MRA is by far the most time-consuming of these imaging techniques (typically requiring 15 minutes or longer for the combined evaluation of the neck vessels and circle of Willis), and the most prone to degradation from patient motion. Given that “time is brain” in the emergent evaluation of stroke, the first goal of this project is to achieve a five-fold or greater decrease in scan time for neurovascular MRA to <3 minutes without the use of contrast agents, while improving reliability using motion-insensitive imaging techniques. Another goal of this project is to develop a rapid protocol for portraying and quantifying intracranial flow patterns and velocities in <30 seconds. We hypothesize that these two goals can be met through the development of two protocols: 1) a highly-accelerated ungated quiescent-interval slice-selective (UnQISS) protocol leveraging radial sampling, real-time motion detection, and simultaneous multi-slice acceleration; and 2) an efficient semi-projective cine arterial spin-labeled (ASL) protocol providing high temporal resolution. A final goal of this project is to test the developed rapid UnQISS and cine ASL protocols in a group of patients with suspected stroke. The expected outcome of this project is a set of rapid protocols for evaluating the neurovascular system in patients with suspected stroke that expeditiously informs the treatment team to guide management decisions regarding medical and endovascular therapy. Since no contrast agents are involved, the developed protocols will be especially useful in the many stroke patients (1 in 3) who present with chronic kidney disease. The specific aims of this project are as follows: 1. To develop and optimize a rapid nonenhanced MRI protocol that provides for anatomical assessment of the intracranial and extracranial vessels (aortic arch to circle of Willis) in <3 minutes. 2. To develop a rapid semi-projective arterial spin-labeling cine technique for displaying and quantifying intracranial flow in <30 sec. 3. In suspected stroke patients, to test the hypotheses that the developed rapid protocols, with respect to currently-used MR protocols, improve image quality, provide more diagnostic information, accurately portray intracranial flow patterns, and decrease scan times.