Evaluation of the effectiveness of transurethral radio frequency hyperthermia in the canine prostate: Temperature distribution analysis

The heating pattern of a transurethral radio frequency (RF) applicator and its induced steady-stare temperature field in the prostate during transuret hral hypothermia treatment were investigated in this study. The specific ab sorption rate (SAX) of the electromagnetic energy was first quantified in a tissue-equivalent gel phantom. It was used in conjunction with the Pennes bioheat transfer equation to model the steady-state temperature field in pr ostate during the treatment. Theoretical predictions were compared to in vi vo temperature measurements in the canine prostate and good agreement was f ound to validate the model. The prostatic tissue temperature rise and its r elation to the effect of blood perfusion Mere analyzed. Blood perfusion is found to be art important factor for removal of heat especially at the high er RF heating level. To achieve a temperature above 44 degrees C within 10 percent of the prostatic tissue volume, the minimum RF power required range s from 5.5 W to 36.4 W depending on the local blood perfusion rate (omega = 0.2-1.5 ml/gm/min). The corresponding histological results from the treatm ent suggest that to obtain better treatment results, either higher RF power level or longer treatment time (>180 minutes) is necessary. This is consis tent with the predictions from the theoretical model developed in this stud y.