Arterial Spin–Labeled Perfusion Imaging to Predict Mismatch in Acute Ischemic Stroke

Abstract

Background and Purpose— We assigned a threshold to arterial spin–labeling (ASL) perfusion-weighted images (PWI) from patients with acute ischemic stroke and compared them with dynamic susceptibility contrast perfusion images to examine whether mismatch can be determined. Methods— Pseudocontinuous ASL was combined with dynamic susceptibility contrast PWI in 23 patients with acute ischemic stroke. Scans were obtained within 24 hours of symptom onset. PWI volumes were defined by ASL cerebral blood flow (<15, <20, and <25 mL/100 g per minute) and dynamic susceptibility contrast–mean transit time (MTT) thresholds (>10 s) that show a strong association with cerebral blood flow <20 mL/100 g per minute in Xenon CT studies. Agreement between the ASL–diffusion-weighted imaging and MTT–diffusion-weighted imaging mismatch and the correlation between penumbra salvage and infarct growth, defined as the difference between the baseline PWI and the baseline diffusion-weighted imaging lesion, respectively, and the final infarct volume were assessed. Results— The lesion volumes defined by MTT>10 s and ASL<20 mL/100 g per minute showed an excellent correlation. There was 100% agreement on the mismatch status between MTT>10 s and ASL<20 mL/100 g per minute. The correlation between infarct growth and penumbra salvage volume was significantly better for PWI lesions defined by ASL<20 mL/100 g per minute and MTT>10 s. Conclusions— In acute ischemic stroke, PWI lesions based on ASL threshold of <20 mL/100 g per minute can provide a reliable estimate of mismatch in correspondence at MTT threshold of >10 s.