Interventional magnetic resonance imaging (MRI) continues to make a profound impact on the practice of neurosurgery. We describe a new MRI modality, diffusion tensor imaging (DTI), which uses the diffusion energy of water to map white matter fibers. DTI has been established in other disorders such as metabolic, demyelinating and ischemic diseases. We describe the use of DTI in identifying white matter tracts such as optic radiations and avoiding them intraoperatively in 2 children with low-grade glial tumors.Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]