Numerical Simulation of the Effect of Temperature- dependent Acoustic and Thermal Parameters on the Focal Temperature and Thermal Lesion of Biological Tissue Irradiated by HIFU

Introduction: Accurate temperature and thermal lesion prediction is very important for high-intensity focused ultrasound (HIFU) in the treatment of tumors. The traditional focal temperature and thermal lesion prediction methods usually use constant acoustic and thermal parameters. However, HIFU irradiation of biological tissue will cause its temperature rise and change the tissue characteristic parameters, which will affect the sound field and temperature field.Material and Methods: The constant acoustic and thermal parameters, dynamic acoustic and thermal parameters, constant acoustic and dynamic thermal parameters, dynamic acoustic and constant thermal parameters were used for simulation by Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation and Pennes biological heat transfer equation (PBHTE), and their effects and differences on the focal temperature and thermal lesion of biological tissue were compared and analyzed.Results: The focal temperature predicted by constant acoustic parameters was less than that predicted by dynamic acoustic parameters, and the thermal lesion area predicted by constant acoustic parameters was also smaller than that predicted by dynamic acoustic parameters. On the premise of using dynamic acoustic parameters, the focal temperature predicted by dynamic thermal parameters was higher than that predicted by constant thermal parameters. When the acoustic parameters remained constant, the focal temperature predicted by dynamic thermal parameters was lower than that predicted by constant thermal parameters, but their predicted thermal lesion areas were almost the same.Conclusion: The temperature-dependent acoustic and thermal parameters should be considered when predicting focal temperature and thermal lesion of biological tissue, so that doctors can use the appropriate thermal dose in the surgical treatment of HIFU.