Use of Arterial Spin Labeling Imaging in Diagnosing and Treating Posterior Cerebral Artery Occlusions.

Objective: Arterial spin labeling (ASL) is a noninvasive MRI technique used to evaluate cerebral perfusion. Arterial transit artifact (ATA), which appears as high-signal areas proximal to vessel occlusion, may provide important diagnostic information, particularly when conventional angiographic visualization is limited. We present two cases of posterior cerebral artery (PCA) occlusion in which ATA detection via ASL played a critical role in guiding endovascular treatment. Case Presentation: Case 1 involved a woman in her 70s who presented with right-sided numbness and visual field loss. MRA did not clearly delineate the left PCA; however, ASL revealed an ATA in the P3-4 territory distal to the angiographically confirmed P2 occlusion. CT perfusion confirmed hypoperfusion, and thrombectomy resulted in complete visual recovery. Case 2 involved a man in his 40s who experienced sudden-onset blindness. MRA indicated bilateral PCA occlusion, and ASL showed bilateral ATA(s). Following intravenous recombinant tissue-type plasminogen activator administration and left PCA thrombectomy, partial visual improvement was observed. On postoperative day 3, ASL again revealed an ATA in the right P3 segment, suggesting reocclusion. Emergency thrombectomy led to visual restoration. Conclusion: These cases highlight the utility of ASL imaging and ATA detection in diagnosing PCA occlusion and monitoring treatment response. ASL provides a noninvasive, contrast-free complement to MRA in the acute stroke setting, particularly for the posterior circulation, where visualization is often limited. ATA may serve as a valuable imaging biomarker for identifying occlusion and reocclusion, aiding clinical decision-making.