Abstract #0224

MR-Guided Focused Ultrasound for the Treatment of Essential Tremor: Initial Experience on MR-Based Targeting and Temperature Monitoring

Yuexi Huang¹, Nir Lipsman², Michael L. Schwartz³, Andres M. Lozano², Kullervo Hynynen¹

¹Sunnybrook Research Institute, Toronto, ON, Canada; ²Division of Neurosurgery, Toronto Western Hospital, Toronto, ON, Canada; ³Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada

Four essential tremor patients have been treated by a MR-guided focused ultrasound brain system (ExAblate 4000) in a phase 1 clinical trial. Treatment target was the ventralis intermediate nucleus (VIM) of the thalamus. Targeting was based on distance measurement from reference structures on a T2 image crossing through the anterior and posterior commissures. Minor adjustments (1mm) were made if patient had sensory response at low power levels. It is crucial to perform temperature mapping on all three orthogonal planes with repeated sonications to detect any irregular shape of the actual focal heating volume. Retrospectively, fractional anisotropy images generated image contrast within the thalamus next to the VIM target, which may be useful for patient specific targeting.