Prediction of the Size of a Thermal Lesion

in Soft Tissue during HIFU Treatment

Kang Il Lee

In focused ultrasound surgery (FUS), high intensity focused ultrasound (HIFU) can be used to destroy pathological tissue deep inside the body without any damage to the surrounding normal tissue. The purposes of this study are to predict the size of the thermal lesion in soft tissue during HIFU treatment by using a concave focused transducer with a circular aperture and to examine the dependence of the size on the sonication and transducer parameters (acoustic intensity, pulse duration, and frequency) and on the tissue properties (attenuation coefficient and perfusion rate). O’Neil’s solution for the pressure field and Pennes’ bioheat transfer equation for the temperature field were employed to simulate the tissue necrosis, and the prediction of the lesion size was based on the evaluation of a 240-min (at 43 °C) thermal dose boundary. It was found that the lesion size could be controlled by adjusting the acoustic intensity, pulse duration, and frequency applied to the tissue. It was also predicted that the lesion size did not strongly depend on either the perfusion rate or the attenuation coefficient of the tissue.