Vivek Buch ^1* David Purger ^1* Anjali Datta ^1* Allen Wang ¹ Daniel Barbosa ² Yosefi Chodakiewitz ¹ Lior Lev-Tov ³ Chelsea Li ¹ Casey Halpern ⁴ Jaimie Henderson ¹ Jennifer A. McNab ¹ Rachelle Rinat Bitton ¹ Pejman Ghanouni ¹

• ¹ Stanford University, Stanford, United States
• ² Medical University of South Carolina, Charleston, South Carolina, United States
• ³ Rambam Health Care Campus, Haifa, Haifa, Israel
• ⁴ Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States

MRI-guided focused ultrasound (MRgFUS) thalamotomy of the nucleus ventralis intermedius (VIM) has emerged as a powerful and safe treatment modality for refractory essential tremor of the hands. While the efficacy of this technique has been extensively described, much remains unclear about how to optimize MRgFUS for patient quality of life (QoL), which may depend as much on a patient's adverse effect profile as on the magnitude of tremor suppression. Diffusion tensor imaging (DTI) has been used to help guide targeting strategies but can pose certain challenges for scalability. In this study, we propose the use of a simplified patient-reported change in QoL assessment to create an unbiased representation of a patient's perception of overall benefit.Further, we propose a large-sample-size, high-resolution, 7T DTI database from the Human Connectome Project to create a normative tractographic atlas (NTA) with representations of ventral intermediate nucleus subregions likely to be structurally connected to the motor cortex.The NTA network-based hotspots are then nonlinearly fitted to each patient's imaging. We found that smaller lesion size and higher extent to which the lesion is within the NTA hotspot predicted patients' assessment of change in QoL at last follow-up. Though long-term change in clinical rating scale for tremor (CRST) impacted QoL, neither intraoperative tremor suppression nor the patient's long-term perception of tremor suppression correlated with QoL. We provide an intraoperative threshold for accumulated dose volume (< 0.06 cc), which along with the networkbased hotspot in the NTA, may facilitate an easily scalable approach to help limit treatment to small, safe yet effective lesions that optimize change in QoL after MRgFUS.