Clinical Importance and Usefulness of Direct Targeting of the Ventral Intermediate Nucleus of the Thalamus Using Fluid and White Matter Suppression Imaging at 3T MRI

BACKGROUND AND OBJECTIVES: Stereotactic targeting of the ventral intermediate nucleus of the thalamus (Vim) in tremor surgery traditionally relies on indirect, atlas-based coordinates, whereas direct visualization of the Vim using advanced MRI sequences has the potential to improve targeting precision and clinical outcomes. We evaluated the feasibility and clinical utility of fluid and white matter suppression (FLAWS) imaging for direct Vim targeting in the MRI-guided focused ultrasound (MRgFUS) procedure. METHODS: We retrospectively reviewed 30 MRgFUS procedures in 29 patients. Cases were divided into conventional indirect targeting (non-FLAWS group, n = 15) and direct targeting (FLAWS group, n = 15). We compared initial targeting accuracy (positive clinical response at the first target location), procedural metrics, and clinical outcomes. RESULTS: The Vim was reliably delineated on FLAWS imaging as a hypointense region at 14.7 ± 1.2 mm lateral (10.7 ± 1.4 mm from the medial border of the thalamus), 7.3 ± 0.7 mm anterior, and 0.4 ± 0.5 mm inferior relative to the posterior commissure, representing a more anterior location (29.2% ± 2.9% of the intercommissural line from the posterior commissure) compared with conventional indirect Vim coordinates. In comparing the 2 targeting strategies, the FLAWS group demonstrated significantly higher initial targeting accuracy (86.7% vs 40.0%; P = .021) and a lower number of target realignments (3.0 vs 6.0; P = .003) than the non-FLAWS group. Regarding clinical outcomes, the FLAWS group exhibited a trend toward a lower incidence of sensory adverse effects (20.0% vs 46.7%) and tremor recurrence (0.0% vs 13.3%) compared with the non-FLAWS group, although this did not reach statistical significance. CONCLUSION: Direct image-based targeting of the Vim using FLAWS imaging at 3T MRI is feasible and offers practical advantages by improving initial targeting accuracy and reducing the need for target realignments in the MRgFUS procedure.