Comparison of dose distribution for radiotherapy and temperature distribution for hyperthermia on a CT slice

An attempt was made to form a theoretical radiation dose-equivalent heat distribution to compare with a sample of calculated temperature distribution of hyperthermia by a radio-frequency (RF) generator, mediated by biological effects. Physical dose distributions for 10 MV X-rays were calculated by computer for treatment planning. Four-portals were used to focus the radiation on the tumor. A CT view of an ovarian tumor was used as a model. The radiation dose distribution was converted to radiation dose equivalent heat-treatment time distribution at 43deg C. The heat-time obtained at 43deg C was further converted to temperature with a fixed treatment time of 60 minutes by a thermal dose equation. From these conversions, temperature distributions were constructed for the dose-distribution of four-portal irradiation. A feasible temperature distribution pattern was obtained by computing RF capacitive heating for the same CT view. This was compared with the temperature distribution derived from four-portal irradiation. The feasible temperature-distribution pattern for RF heating indicated a similar but better distribution in the tumor center and in the surrounding normal tissue, except at the tumor edge. These results indicate need of biological consideration for dose distribution of different modalities. Additional relevant studies of thermal sensitivity of human cells, and normal and tumor tissue are encouraged to determine sensitivity and obtain possible predictive thermal doses for which the biological effects should be taken into account. (author)