Measurement of oxygen extraction fraction (OEF) provides important information about tissue oxygen utilization. OEF maps can be obtained using a double echo asymmetric spin echo (ASE) sequence. Partial volume effect may lead to inaccurate OEF measurements in regions with mixed tissue types. We introduced a local linear regression algorithm to correct for partial volume effect. The PVC OEF method reduced model fitting errors and signal contamination of CSF, and it improved the association between OEF and WMH lesion burden.