Key points	Inflammatory cells and bacteria within an abscess core restrict diffusion
Pearls	ADC values and morphology within the area showing restricted diffusion may help in differentiating abscess from tumour and pyogenic from fungal abscess The location of diffusion restriction may orientate in the aetiology of viral encephalitis: limbic system for herpes simplex; splenium of the corpus callosum for influenza and Epstein-Barr viruses; thalami for West Nile virus DWI most sensitive technique in the early stages of CJD
Pitfalls	Subacute haematoma can look like an abscess