Ultrasonic and biothermal numerical models for a simplified 3D chest wall anatomy were developed for a more accurate analysis of power deposition patterns and resulting temperature distributions during hyperthermic therapy of recurrent breast cancer. Four different media were considered: water, muscle tissue, bone tissue (ribs and cartilage), and lung tissue. Results are presented for planar insonation at normal incidence in a typical chest wall section at 1.0 and 3.5 MHz; frequencies that are routinely used clinically. Transient profiles show that the initial rate of temperature rise in bone tissue is much larger than in muscle tissue; however, the temperature difference between these two media decays after the first two minutes of insonation. Steady state results showed that the highest temperatures were induced at the soft tissue-bone interfaces and inside the bone tissue at 1.0 MHz, while at 3.5 MHz these were located in the muscle tissue a few mm in front of the bone. Strategies for treatment planning and optimization are discussed.
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