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.