ULTRASOUND THERMOTHERAPY OF BREAST: THEORETICAL DESIGN OF THE TRANSDUCER AND NUMERICAL SIMULATION OF THE PROCEDURE

Purpose: The absorbed energy of ultrasound is changed into heat in a dissipative medium. This could be of great advantage in treating tumors in a non-invasive manner by raising their temperature to cytotoxic levels. This study investigates whether using a fixed-focus transducer could destroy breast tumor cells at early stages in a cost effective manner which reduces the treatment time significantly.

Methods and Materials: An appropriate fixed-focus transducer was designed and the resultant acoustic pressure has been calculated using rayleigh integral. A rael two dimensional breast model has been constructed from a cancerous breast MRI. Then the generated temperature elevation has been calculated using bioheat equation applying finite element method on the model.

Results: Results demonstrate that using this transducer could generate a temperature of up to 62 degrees centigrade in 3 seconds of sonication. The region in which the peak temperature is obtained is in the center of the tumor and the cytotoxic temperature is generated throughout the tumor while leaving the normal tissue in a safe thermal position.

Conclusions: This temperature elevation is enough to destroy cancer cells by satisfying the required thermal dose. The region in which the cytotoxic temperature is generated is small enough to destroy cancer cells at early stages. The short treatment time would deacrease the effect of perfusion and could increase the safety by taking advantage of minimum patient movement. Also the area of normal tissue that exceeds the threshold of thermally induced pain is minimum.