LIFU Mechanisms for PTSD in Healthcare Workers

Inclusion Criteria: 1. Adults in a frontline healthcare position (e.g. emergency medical services) 2. Ages 18-65 years 3. PTSD Checklist for DSM-5 (PCL-5) score ≥ 33 and \< 65, OR at least partial PTSD as measured by the MINI 4. English proficiency as evaluated by language ability during screening Exclusion Criteria: 1. Neurological disorders 2. DSM-5 diagnosis of psychotic disorders, eating disorder, obsessive-compulsive disorder, moderate to severe alcohol or substance use disorder within the past year, bipolar disorder, or major depressive disorder with psychosis 3. Suicidal intent or plan (as measured by Suicide-Risk-Assessment-C-SSRS "Yes" answers to items 3, 4 or 5 of Suicidal Ideation-Past 1 month section, or any "Yes" answer to any of the items of Suicidal Behavior-Past 3 months section), or any suicide attempt in the last 3 months. 4. History of severe traumatic brain injury (as indicated by score ≥ 3 on the Tulsa Head Injury Screen) or of skull fractures 5. Contraindications to MRI as determined by the MR Environment Screening 6. Pregnancy, determined by urine pregnancy test administered prior to every MRI scanning procedure 7. Evidence of inability to comply with study procedures based on experimenter judgement. 8. Change in the dose or prescription of a medication within the 6 weeks before enrolling in the study that could affect brain functioning, e.g., anxiolytics, antipsychotics, antidepressants, benzodiazepines, or mood stabilizers. 9. Non-correctable vision or hearing problems 10. Unstable medical diagnoses 11. Any structural abnormalities in the LIFU target region on screening brain MRI.