D. Louis Collins, PhD, is a professor in neurology and neurosurgery and in biomedical engineering, an associate member of the Center for Intelligent Machines at McGill University, and an associate member of the McGill Centre for Studies in Aging. His laboratory develops and uses computerized image processing techniques such as non-linear image registration and model-based segmentation to automatically identify structures within the human brain. These techniques are applied to a large base of magnetic resonance (MR) data from normal subjects to quantify anatomical variability. In image-guided neurosurgery (IGNS), these techniques provide the surgeon with computerized tools to assist in interpreting anatomical, functional and vascular image data, permitting the effective planning and execution of minimally invasive neurosurgical procedures. Automated atlasing is essential in IGNS for thalamotomy and pallidotomy in the treatment of Parkinson’s disease, or temporal-lobe depth electrode implantation in the diagnosis of epilepsy, since tissue targets in these procedures cannot be viewed directly on MR. Computerized atlasing minimizes trauma to the patient and allows resection of the smallest amount of brain tissue necessary for effective therapeutic treatment.