The proposed study is to evaluate the safety and initial efficacy of MRgFUS for patients with treatment-refractory OCD. This study is designed as a prospective, single arm, nonrandomized study. Assessments will be made before and after MRgFUS for adverse events related to treatment, for clinical symptom relief, and quality of life (QoL). The target in the brain chosen for ablation will be the anterior limb of the internal capsule (ALIC) (i.e 'capsulotomy'). Safety will be assessed prospectively in radiologic and clinical terms. Post-procedural imaging will be evaluated for evidence of swelling, hemorrhage, and the evolution of the lesion in the anterior limb of the internal capsule. Patients will be clinically followed up at Day 1, Month 1, Month 3, Month 6 and Month 12 post-procedure. At every follow-up visit, patients will be evaluated for general health, neurological changes, as well as for device/procedure related adverse events. Imaging will also be performed with positron emission tomography (PET) and MRI, as per the Month 3 and Month 12 post-procedure. Feasibility will be evaluated by determining the rate of patient accrual, the tolerability of the procedure for patients, and the technical ability of heating the ALIC to lesional temperatures.