Optimization of volumetric MR-guided high-intensity focused ulatrsound ablations in moving organs

Introduction In this work, a method for the optimization of volumetric MR-guided high intensity focused ultrasound (HIFU) ablations is presented. While commonly MRguidance of thermal therapies is based on temperature control the on-line assessment of the thermal dose has been suggested to determine the therapy endpoint [1]. Therefore, we propose to monitor the thermal dose [2] of the treated tissue to ensure a complete destruction of the tumor tissue. The short positioning time of modern ultrasound transducer systems as compared to the acquisition time of an MR-thermometry image enables the treatment of several points between successive images. Optimizing this trajectory of ablation points [3] in combination with a 3D motion correction technique [4,5] allows for an effective destruction of the target tissue with minimal energy, time and damage outside the target area. The feasibility of the proposed method was tested experimentally ex vivo under conditions simulating respiratory movement of abdominal organs.