Inflammation of the brain is suspected to be present in children with PANDAS, but confirming this hypothesis is difficult. The best tools for revealing brain inflammation expose patients to ionizing radiation, yet these approaches are limited for use, especially in children. Dr. Williams and his team will use a new and innovative technique to measure inflammation with MRI, which emits no ionizing radiation. His study will compare children with PANDAS to children with pediatric-onset (non-PANDAS) OCD, as well as healthy children, to further our understanding of the role that inflammation plays in PANDAS.