Magnetic resonance images showing the usefulness of diffusion weighted images (DWI) and apparent diffusion coefficient (ADC) maps to distinguish pyogenic abscess from cystic or necrotic brain tumor. Upper : Left occipital mass lesion shows a high signal intensity on DWI and low signal intensity on ADC mapping, which is diagnosed to cerebral abscess. Lower : Right occipital mass lesion shows a low signal intensity on DWI and hign signal intensity on ADC mapping, which is diagnosed to glioblastoma.