Count-based PET method for predicting ischemic stroke in patients with symptomatic carotid arterial occlusion

PURPOSE: To test the ability of a count-based positron emission tomographic (PET) method, without arterial sampling, for the measurement of regional c erebral oxygen extraction fraction (OEF) to predict ischemic stroke in pati ents with symptomatic carotid arterial occlusion. MATERIALS AND METHODS: The outcome analysis of a blinded prospective study designed to determine if increased OEF was an independent predictor of stro ke in patients with symptoms and with carotid occlusion was repeated by sub stituting a count-based method of OEF measurement for the original quantita tive technique. The performance of the quantitative and count-based methods was assessed by using Kaplan-Meier cumulative survival functions (log-rank , [P < .05]). Receiver operating characteristic (ROC) curves for both metho ds were generated. RESULTS: Thirteen ipsilateral strokes occurred during a mean follow-up of 3 .1 years for 81 patients. All ipsilateral strokes occurred in 50 patients w ith increased count-based OEF (P = .002, sensitivity 100%, specificity 46%) . Sixty-eight patients underwent complete quantitative studies, which allow ed comparison of OEF methods. Both the count-based and the quantitative met hods were predictive of stroke in this subgroup (P = .005 and .025, respect ively). ROC analysis demonstrated a greater area under the curve for the co unt-based OEF method. CONCLUSION: Count-based PET measurement of OEF without arterial sampling ac curately predicts stroke in patients with carotid occlusion.