Abstract W P40: Predicting Tissue at Risk for Infarction Within an Optimal Arterial Spin Labeling Cerebral Blood Flow Threshold in Patients with Acute Stroke

Abstract

Background: and Purpose: The aim of this study was to investigate whether pseudo-continuous arterial spin-labeling (ASL) in combination with an appropriate cerebral blood flow (CBF) threshold can reliably detect tissue at-risk for infarction. Methods: The retrospective study included 50 patients with acute stroke in the middle cerebral artery (MCA) territory who underwent perfusion-weighted magnetic resonance imaging (PW-MRI) within 24 hr of symptom onset and again in the subacute phase. After image co-registration the core and mismatch were segmented on ASL maps. Receiver operating characteristic (ROC) curve analysis was performed to calculate the optimal ASL-CBF threshold. Volumes on PW-MRI were recorded based on their ASL-CBF threshold (≧19-, 20-, 21-, 22-, 23-, 24- and 25 sec). Then the correlation between the penumbral salvage area and infarct growth, defined as the size difference between the lesion on baseline PWI- and the baseline diffusion-weighted images, and the final infarct volume were determined. Results: ROC analysis showed that the optimal threshold was 21.2 mL/100 g/min (area under the curve 0.88). The correlation between infarct growth and the penumbra salvage volume was significantly better for PWI lesions defined by ASL≦21 mL/100 g/min (r=-0.66; p<0.001). In 9 patients without recanalization on MRI obtained in the subacute phase, the ASL≦21 mL/100 g/min threshold more closely predicted the final infarct volume (r=0.82; p=0.006). Conclusion: PWI (ASL≧21 ml/100 g/min) volumes may provide an approximation of the volume of tissue at-risk for infarction in patients with acute stroke in the MCA territory.