Safety and Feasibility of FUS Next Generation Dome Helmet (NGDH) to Perform Neuromodulation in Patients With Treatment Refractory Obsessive Compulsive Disorder (OCD)

Inclusion Criteria: 1. Must be deemed to have the capacity to provide informed consent. 2. Age 18 to 85 years. 3. Diagnosis of obsessive-compulsive disorder according to DSM-5 criteria. 4. Yale-Brown Obsessive Compulsive Scale total score greater than 22. 5. If taking psychiatric medications, must be on a stable regimen for at least 30 days before enrollment. Psychiatric medications will be continued throughout the study. 6. Previous trial of at least two first-line antidepressant agents at an adequate dose and duration, as assessed by two psychiatrists. 7. Previous trial of cognitive behavioural therapy or psychotherapy for OCD for at least 6 weeks. Exclusion Criteria: 1. Pregnant or intending to become pregnant during the study. 2. Substance use disorder, other than cannabis or nicotine use disorder, of moderate severity or greater, or where the substance is the primary substance of concern, according to DSM-5 criteria. 3. Known active seizure disorder or significant head injury with an imaging-confirmed lesion. 4. Unstable medical illness. 5. Not eligible for 3-Tesla MRI, such as due to an MRI-incompatible pacemaker or other implanted device. 6. Unable to reliably attend the required screening, treatment, and follow-up visits. 7. Severe claustrophobia that would prevent MRI scanning. 8. History of a bleeding disorder or coagulopathy. 9. Anticoagulant therapy or use of medications known to increase the risk of hemorrhage within the required washout period before treatment, including: * Antiplatelet agents or vitamin K antagonist anticoagulants within 7 days of treatment * Non-vitamin K oral anticoagulants within 72 hours of treatment * Heparin-derived compounds within 48 hours of treatment