The goal of this clinical trial is to evaluate the safety and initial effectiveness of Magnetic Resonance-guided focused ultrasound neuromodulation using the Next Generation Dome Helmet (NGDH) device in patients with treatment-resistant depression. This is a prospective, single-arm, non-randomized study.

Participants will:

• Undergo two focused ultrasound treatment sessions targeting nodes of the cortical-striatal-thalamic circuit (CSTC) , spaced four weeks apart.
• Return for follow-up visits at 24 hours, 2 weeks, and 4 weeks after each treatment session, during which clinical scales and imaging assessments will be conducted to monitor safety and clinical effects.

A total of 20 participants with treatment-resistant depression will be enrolled and treated in this study. Participants will be recruited through local psychiatric practices, referrals from participating institutions, and external referrals, including both physician and self-referrals.

Eligibility will be assessed during a dedicated screening appointment conducted by the study coordinator in collaboration with a study-affiliated physician. The anticipated enrollment period is approximately two years, beginning from the date of first patient enrollment to the enrollment of the final participant.

Inclusion Criteria:

1. Deemed to have the capacity to provide informed consent.
2. Aged between 18 and 65 years.
3. Diagnosis of major depressive disorder (MDD) according to DSM-5 criteria.
4. Total score >20 on the Hamilton Depression Rating Scale (HAMD-17).
5. On a stable regimen of psychiatric medications for at least 30 days prior to enrollment.
6. Documented previous trial of at least two first-line antidepressant agents at adequate dose and duration, as assessed by two psychiatrists.
7. Documented previous trial of cognitive behavioral therapy (CBT) or psychotherapy for MDD, sustained for at least 6 weeks.

Exclusion Criteria:

1. Pregnant or intending to become pregnant during the study period.
2. Diagnosis of a substance use disorder (excluding cannabis or nicotine) of moderate severity or greater, or when the substance is the primary focus of treatment, based on DSM-5 criteria.
3. Known active seizure disorder, significant head injury with an imaging-verified lesion
4. Unstable medical illness.
5. Not eligible for 3-Tesla MRI (i.e. MRI-incompatible pacemaker)
6. Inability to reliably attend required screening, treatment, or follow-up appointments.
7. Severe claustrophobia, as identified by the participant, that would prevent completion of MRI procedures.