Abstract Thirty percent of epilepsy patients have seizures despite best medical therapy. Continued seizures and polypharmacy are associated with poor quality of life. While epilepsy surgery has emerged as a promising treatment for these patients, surgical outcomes have not significantly improved over the years. These stagnant outcomes can be attributed to poor seizure onset zone (SOZ) and epileptic network (EN) localization with currently available tools. Epilepsy as a disease of energy metabolism has emerged as a relatively novel concept with several studies suggesting upregulation of lactate within epileptic brain. Using patient tissue and epilepsy models, our lab recently showed that when neurons are chronically activated, they begin to use glycolysis as a primary means of cellular energy metabolism, thus upregulating the production of lactate. Furthermore, we recently introduced magnetic resonance imaging (MRI) of hyperpolarized (HP) 13C pyruvate as a novel imaging tool to spatially and temporally localize its downstream metabolic products, including lactate, in glioma and traumatic brain injury. In this proposal we combine this novel technology with our previous findings of elevated lactate production in epileptic tissue to explore hyperpolarized 13C MRI (hpMRI) as a means to identify epileptic tissue. Our overarching hypothesis is that hpMRI of pyruvate will accurately identify elevated lactate production in a rat model of focal epilepsy and in resected epileptic tissue ex vivo. In our first Aim we will use a lithium pilocarpine rat model of temporal lobe epilepsy to explore the ability o f[1-13C]pyruvate hpMRI to identify elevated lactate in vivo. In our second Aim, we will determine if MRS of HP [1-13C]pyruvate is able to identify elevated lactate in resected human epileptic tissue ex vivo. These data will provide the pre-clinical evidence necessary for a clinical trial evaluating the efficacy of 13C hpMRI as a tool to identify epileptic tissue in patients.