Intra-arterial high signals on arterial spin labeling perfusion images predict the occluded internal carotid artery segment

Introduction
Arterial spin labeling (ASL) involves perfusion imaging using the inverted magnetization of arterial water. If the arterial arrival times are longer than the post-labeling delay, labeled spins are visible on ASL images as bright, high intra-arterial signals (IASs); such signals were found within occluded vessels of patients with acute ischemic stroke. The identification of the occluded segment in the internal carotid artery (ICA) is crucial for endovascular treatment. We tested our hypothesis that high IASs on ASL images can predict the occluded segment.
Methods
Our study included 13 patients with acute ICA occlusion who had undergone angiographic and ASL studies within 48 h of onset. We retrospectively identified the high IAS on ASL images and angiograms and recorded the occluded segment and the number of high IAS-positive slices on ASL images. The ICA segments were classified as cervical (C1), petrous (C2), cavernous (C3), and supraclinoid (C4).
Results
Of seven patients with intracranial ICA occlusion, five demonstrated high IASs at C1–C2, suggesting that high IASs could identify stagnant flow proximal to the occluded segment. Among six patients with extracranial ICA occlusion, five presented with high IASs at C3–C4, suggesting that signals could identify the collateral flow via the ophthalmic artery. None had high IASs at C1–C2. The mean number of high IAS-positive slices was significantly higher in patients with intra- than extracranial ICA occlusion.
Conclusion
High IASs on ASL images can identify slow stagnant and collateral flow through the ophthalmic artery in patients with acute ICA occlusion and help to predict the occlusion site.

内容要旨・審査要旨・論文本文の公開
本論文は, 著者Shu Sogabeの学位論文として提出され, 学位審査・授与の対象となっている。
This is a post-peer-review, pre-copyedit version of an article published in Neuroradiology. The final authenticated version is available online at: https://doi.org/10.1007/s00234-017-1828-9