Prediction of Temperature Distribution and Volume of Lesion During HIFU Therapy

Ultrasound hyperthermia is used to treat tumors in human tissue by heat. It is characterized by the application of high intensity focused ultrasound (HIFU), high local temperatures and short treating time of a few seconds. HIFU is a non-invasive treatment modality for a variety of cancers, including breast, prostate, kidney, liver, bone, uterus, and pancreatic cancers. Computer models have been used to determine tissue temperatures during ultrasound hyperthermia. In this work, we consider a liver tissue with a tumor at its center. We calculated temperature distribution in the presence a large blood vessel. We studied the effect of varying the exposure time (heating duration) and the diameter of the blood vessel. In the present work, simulations were performed to predict the volume and position of lesion induced by HIFU. We used the Pennes bioheat equation for modeling heat transfer. A finite element method (FEM) was used to obtain the temperature distribution for a heat transfer equation. A 3-D model for simulation of tumor tissue utilized a cylinder located in the center of the cylindrically modeled liver tissue. The study proved that as the vessel diameter was reduced, the temperature of the tumor was increased and also with the use of the more exposure time, the temperature at the centre of tumor increased. The heating duration and absorbed power density are important factors in lesion forming.