Thermal therapy is a type of cancer treatment in which body tissue is exposed to high temperature, to damage and kill cancer cells. The lesion induced by a single high intensity focused ultrasound (HIFU), namely a heated necrotic element or biological focal region is the foundation for the HIFU ablation of a tumor mass. In this paper, the pressure field induced by HIFU transducer was solved using ONeill’s equation. The temperature distribution was simulated by solving the Pennes’ bioheat transfer equation. The effects of different ultrasound parameters, such as sound intensity, exposure time and ultrasound frequency, on the heated necrosis element are investigated. Numerical results show that with increasing exposures, the heated necrosis element increases, but its contour becomes plumper and increasing the ultrasound frequency or the outer radius of the spherical transducer leads to decrease in the heated necrosis volume.

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