Abstract
To analyze and compare direct and indirect targeting of the Vim for MRgFUS thalamotomy. We retrospectively evaluated 21 patients who underwent unilateral MRgFUS Vim ablation and required targeting repositioning during the procedures. For each patient, in the three spatial coordinates, we recorded: (i) indirect coordinates; (ii) the coordinates where we clinically observed tremor reduction during the verification stage sonications; (iii) direct coordinates, measured on the dentatorubrothalamic tract (DRTT) at the after postprocessing of DTI data. The agreement between direct and indirect coordinates compared to clinically effective coordinates was evaluated through the Bland–Altman test and intraclass correlation coefficient. The median absolute percentage error was also calculated. Compared to indirect targeting, direct targeting showed inferior error values on the RL and AP coordinates (0.019 vs. 0.079 and 0.207 vs. 0.221, respectively) and higher error values on the SI coordinates (0.263 vs. 0.021). The agreement between measurements was higher for tractography along the AP and SI planes and lower along the RL planes. Indirect atlas-based targeting represents a valid approach for MRgFUS thalamotomy. The direct tractography approach is a valuable aid in assessing the possible deviation of the error in cases where no immediate clinical response is achieved.
Highlights
To analyze and compare direct and indirect targeting of the Vim for Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) thalamotomy
All functional neurosurgical procedures are directed to specific anatomical areas involved in the neurofunctional circuits of motion control; the intermediate ventral nucleus (Vim) of the thalamus is one of the main targets of choice for patients with essential tremor (ET) and patients with tremorgenic P D5, 6
The mean values of the target repositioning along the x, y, and z coordinates were respectively 0.66 mm along the RL plane, 0.48 mm along the AP plane, and 0.32 mm along the SI plane
Summary
To analyze and compare direct and indirect targeting of the Vim for MRgFUS thalamotomy. Indirect atlas-based targeting represents a valid approach for MRgFUS thalamotomy. This method, being carried out based on anatomical landmarks (namely the anterior and posterior commissure, AC-PC), is not patient-specific and is relatively insensitive to interindividual anatomical v ariations[11,12,13,14]. Regarding Vim targeting, there is a growing body of literature that recognizes MR diffusion tensor imaging (DTI) with tractography of the dentatorubrothalamic tract (DRTT) as one of the most valid methods for in vivo imaging v isualization[16, 17]. Few studies have investigated the actual error of the two techniques by directly comparing tractography-based targeting and atlas-based Vim targeting
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