Hyperthermia as a modality for the treatment of numerous types of cancers continues to show promise for clinical use, especially when used synergistically with low dosage x-rays. Methods of heat deposition include microwave, radio frequency, and ultrasound. To date, none is able to transmit the correct amount of heat to the tumor site with minimal interference to normal tissue in a controlled way. As a result, hyperthermia treatment of deep tumors has been largely ignored.A scanning focused beam ultrasound hyperthermia delivery system has been developed for the treatment of deep tumors. This system features temperature monitoring within the tumor volume using thermocouples, flying-spot heating, and continuous recording of important parameters. Critical to the successful implementation of this system is the development of models that can provide real-time 3-D temperature profiles. These models must include temperature data at selected points, and provide for real-time feedback control by intensity modulation of the ultrasonic beam.The method under development is to adopt simple models that retain the basic heat transfer processes and geometry and yet allow approximate techniques, such as the method of weighted residuals, to be applied for the solution. Considerable attention will be placed on handling blood flow and the power source term, which becomes temperature dependent by virtue of the feedback control. Progress to date shows the approach to be sound. The proposed research is crucial for the successful implementation of a sophisticated hyperthermia delivery system for clinical use. Simple I-D models already developed by the researchers will be extended to 3-D and to geometries more representative of in vivo tumors. The new hyperthermia system will be clinically evaluated during Phase 11.National Cancer Institute
