The goal of this clinical trial is to evaluate whether low-intensity focused ultrasound (LIFU) of the ventral anterior cingulate cortex (vACC) can normalize dysfunctional brain activation patterns and behaviors in frontline healthcare workers with post-traumatic stress disorder. The main questions it aims to answer are: * Does LIFU of the vACC effect activity and connectivity of the vACC and amygdala? * Does LIFU of the vACC reduce post-traumatic stress symptoms? Researchers will compare LIFU to sham modulation to see if LIFU modulates activity of vACC-amygdala circuitry and affects threat sensitivity and emotion regulation. Participants will: * Complete two fMRI sessions (before and after LIFU) * Receive a single session of LIFU or sham modulation of the vACC * Wear a wearable device that tracks sleep and heart rate metrics