Abstract
Ultrasound hyperthermia has become one of the new therapeutic modalities for breast cancer treatment, since ultrasound appears to selectively affect malignant cells without causing any deleterious effects to the surrounding normal tissues. The main objective of this study is to numerically simulate the interaction of therapeutic ultrasound with a multi-tissue type system, and to develop an analytical model for calculating the temperature rise in these tissues due to ultrasound. First, the finite-element method has been used to compute the radiated power density produced by a circular ultrasonic transducer disk, the heat deposition in each of the biological tissues and the 2-D temperature distribution during ultrasound hyperthermia. Second, an analytical model was developed in which a modified heat transfer equation was used to compute temperature profiles in different tissues. The therapeutic transducer was employed at three different frequencies of 0.75, 1.5 and 2.75 MHz and simulations were allowed to run from 180 to 300 seconds, for a focal depth 10 cm below the surface of the breast tissue. Numerical results of the temperature distribution in different tissues were compared with analytical calculations. The results show that employing a transducer at a frequency of 1.5 MHz is the most suitable for a successful ultrasound therapy in this application.