Clinical Utility of CMRO2 Obtained with MRI in Determining Ischemic Brain Tissue at Risk

P16 It has been suggested that the relationship between oxygen delivery and oxygen demand defines brain tissue at risk during cerebral ischemia. We have recently demonstrated that a quantitative estimate of cerebral blood oxygen saturation (and thereby oxygen extraction fraction, OEF) can be obtained using MRI in vivo. When combined with MR estimated cerebral blood flow (CBF), a quantitative measure of MR-CMRO2 can be calculated. In this study, we sought to explore the potential clinical utility of MR-CMRO2 in determining brain tissue at risk during cerebral ischemia. Seven patients with acute ischemic strokes were imaged at 4.5±.9 hrs (tp1) and 6 of the patients were imaged 3–5 days after stroke onset (tp2) with diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). In addition, a 2D multiecho gradient/spin echo sequence was employed to acquire images which were subsequently used to estimate MR-OEF. Singular value decomposition was used to obtain a quantitative estimate of CBF to calculate MR-CMRO2 (= MR-OEF x MR-CBF). At tp1, 5/7 patients showed a DWI-PWI mismatch (PWI>DWI) while 2/7 patients exhibited match. At tp2, only 1 patient showed PWI