Rapid, robust and non-invasive cerebral oxygenation measurements using MRI R01NS082561-02. Oxygen extraction fraction (OEF) is an important cerebral oxygen metabolic parameter that provides critical information for understanding the pathophysiology of cerebrovascular disease, predicting tissue infarction and patient outcome, and may identify patients who will benefit from therapeutic intervention. It has been demonstrated that elevation of oxygen extraction fraction (OEF) in brain tissue portends a 6-7 fold increased risk of subsequent stroke in patients with chronic atherosclerotic carotid artery occlusion. This project will develop a rapid, robust and accurate, and noninvasive MR OEF measurement technique. In addition, MR OEF measurements will be validated against simultaneous 15O PET OEF measurements using an integrated PET and MR system. The success of this project can fill a major gap between real-world clinical need and the capability of the current MR imaging techniques in OEF measurements and will have a great impact on appropriate patient diagnosis and treatment for cerebrovascular disease. P.I.: Hongyu An.