[Diffusion-weighted MR imaging of the breast]

Diffusion-weighted imaging is helpful to further characterize lesions that remain indeterminate after morphological and dynamic MR evaluation. Suspicious lesions are hyperintense on diffusion-weighted images with corresponding low ADC values, indicating restricted diffusion and hypercellularity. Benign lesions and tumors responding to treatment usually have no diffusion restriction. ADC maps are useful for T2W hyperintense lesions that could mask the presence of restricted diffusion. Image fusion is sometimes needed to accurately localize enhancing lesions on ADC maps. For indeterminate lesions, a hypocellular appearance suggests a lower ACR category whereas the presence of restricted diffusion suggests a higher category.