The purpose of this proposal is to develop techniques for thermal dosimetry in tissues subjected to hyperthermia. The attainment of this goal requires both experimental and theoretical efforts. This application is concerned primarily with the former, although some numerical studies are included. Thermal dosimetry can be divided into five aspects. (i) Comparative thermal dosimetry deals with determining the general heating characteristics of various modalities in order to establish which classes of tumors can be heated by each method and configuration. (ii) Prospective thermal dosimetry (treatment planning) is the determination of the best modality or configuration for treating a specific tumor in a real patient. Proper dielectric and thermal properties are assigned to anatomical regions determined from a CT scan. The appropriate power deposition pattern (SAR), determined from phantom experiments or from theorectical calculations, is superimposed upon the anatomical map. A bioheat transfer calculation is performed using idealized, bracketing case thermal models with blood flow as an adjustable parameter. Thus thermal profiles are generated which predict the best and worst heating patterns to be expected and the preferred locations for thermometer probes are selected. (iii) Concurrent thermal dosimetry is the real time monitoring and control of the treatment or experiment. Computerized data acquisition systems coupled to multiple sensor thermometer probes are necessary for this aspect. Temperatures, heating and cooling transients, net power, and patient parameters must be recorded and displayed in real time to assure efficacy and safety. (iv) Retrospective thermal dosimetry consists of normalizing the thermal models to the clinical or experimental data in order to determine the temperature distributions throughout the region even where no thermometers were located. From the data, thermal dose profiles can be computed as well as estimates of the blood flow distributions. (v) Physiological consequences of the therapy include changes in blood flow during the treatment as a response to high temperatures, vascularity changes over periods of days as a response to heat shock, and changes in thermal properties as a prognosticator of effective therapy.
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