Differences between Acute Embolic and Atherosclerotic Middle Cerebral Artery Occlusion in Multiphase Arterial Spin-labeling Imaging

Arterial spin-labeling magnetic resonance imaging (ASL-MRI) is widely used for evaluating collateral development in patients with acute ischemic stroke (AIS). This study aimed to characterize the findings of multiphase ASL-MRI between embolic and atherosclerotic large vessel occlusion (LVO) to aid in the differential diagnosis. Among 982 patients with AIS, 44 who were diagnosed with acute, symptomatic, and unilateral occlusion of the horizontal segment of the middle cerebral artery (MCA) were selected and categorized into embolic stroke (ES) and atherosclerosis (AT) groups. Using ASL-MRI (postlabeling delay [PLD] of 1.5, 2.0, and 2.5 s) at admission, the ipsilateral to contralateral ratio (ICR) of the signal intensity and its time-course increasing rate (from PLD 1.5 to 2.0 and 2.5, AICR) were measured and compared between the two groups. The mean ICR was significantly higher in the AT group than in the ES group (AT vs. ES: 0.49 vs. 0.27 for ICR1.5, 0.73 vs. 0.32 for ICR2.0, and 0.92 vs. 0.37 for ICR2.5). The AICR of PLD 1.5-2.0 (AICR2.0) and 2.5 (AICR2.5) were also significantly higher in the AT group than in the ES group (AT vs. ES: 50.9% vs. 26.3% for AICR2.0, and 92.6% vs. 42.9% for AICR2.5). Receiver operating characteristic curves showed moderate-to-strong discriminative abilities of each ASLMRI parameter in predicting MCA occlusion etiology. In conclusion, multiphase ASL-MRI parameters may aid in differentiating intracranial LVO etiology during the acute phase. Thus, it is applicable to AIS management.