Diffusion-weighted imaging to assess treatment response in a child with trilateral retinoblastoma.

Trilateral retinoblastoma (TRb) is a rare condition in which children with bilateral retinoblastoma develop primary midline intracranial neuroblastic tumors. The intracranial lesions are difficult to follow after treatment due to residual mass-like enhancement that may represent persistent tumor or treated disease. We highlight a case where close evaluation of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) characteristics accurately depicted the extent of treated disease versus residual tumor after chemotherapy.