The current study looks to extend the neuroimaging investigation using anatomic white matter targeting, functional gray matter targeting and changes in changes in regional glucose metabolism of Deep Brain Stimulation (DBS) in severe obsessive-compulsive disorder (OCD) with the long-term aim of identifying biomarkers that could improve outcomes of this expensive and invasive therapy. Improved imaging would allow surgeons to place the DBS lead closer to the biological targets, thus improving efficacy of the treatment.