Transcranial magnetic resonance-guided focused ultrasound (tcMRgFUS) is an effective and safe treatment option for medically refractory essential tremor (ET). Like any other thermal ablation modality, the effectiveness of ultrasound thalamotomy relies on the accuracy of acoustic energy deposition in the target area. However, the presence of an intact skull disturbs the propagation of the ultrasound beam through the brain by inducing phase aberrations and energy attenuation. The degree of inaccuracy on thermal lesioning is considered patient-dependent, and the desired beam corrections demand information on patient-specific acoustic properties at the voxel level. To date, there is no satisfactory methodology that correlates patients skull morphology and achieved focal temperature distribution. Therefore, this proposal aims to address some of the treatment planning challenges by retrospectively investigating the thermal maps of a group of patients underwent to tcMRgFUS thalamotomy at Brigham & Women's Hospital. The intent is to re-create the clinical setting numerically and to optimize a collection of patient-specific acoustic properties that best represent the physical outcome. Thus, the specific aims proposed here are: 1) retrieve the full treatment setup and elaboration of the patient-specific thermal map; 2) analysis of the volumetric spatial distribution of the temperature at the focal area and establishment of relations with any skull lesion location; 3) implementation of a 3D acoustic simulation in combination with optimization algorithms for skull properties determination. The overall goal here is to provide a better understanding of the patient-specific acoustic properties and to contribute to improving the quality of pre-treatment planning, reduction the risk of bone marrow necrosis and pain during the procedures. The knowledge acquires here can also be valuable for all other ultrasound transcranial applications.
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