Abstract
During high intensity focused ultrasound (HIFU) therapy, the operation parameters are usually kept the same for each treatment spot. Because of the thermal diffusion from nearby spots, the lesion size will gradually increase. In this study, an algorithm was developed to determine the number of HIFU pulses delivered to each spot for uniform lesion production. The exposure energies required using different scanning pathways, spot spacing and motion time were compared with each other. It is found that spiral scanning from the outside to the center with spot spacing of 2 mm and motion time less than 10 s needs the least numbers of pulses or HIFU energy in uniform lesion production with the minimal temperature elevation. Effects of thermal properties of tissue (i.e., specific heat capacity, convective heat transfer coefficient and thermal conductivity) on HIFU ablation were investigated to determine the corresponding treatment planning. Uniform lesion production in the gel phantom and ex vivo bovine liver using the proposed algorithm was accord with the simulation. Therefore, dynamically adjusting ultrasound exposure energy can improve the efficacy and safety of HIFU ablation, and the treatment planning depends on the scanning protocol and thermal properties of the target.
Published Version
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