This study evaluates the safety, feasibility, and preliminary efficacy of focused ultrasound (FUS) neuromodulation delivered using the Next Generation Dome Helmet (NGDH) in participants with treatment-refractory obsessive-compulsive disorder (OCD). Participants will undergo two study sessions, four weeks apart, involving active FUS neuromodulation targeting nodes of the cortico-striato-thalamo-cortical (CTSC) circuit. Outcomes include adverse events, changes in OCD symptom severity, and quality of life.