Abstract

The heating pattern of a radio frequency (RF) electrode catheter and its induced temperature field in prostate during transurethral thermal therapy treatment were investigated in this study. Experiments were performed in a tissue-equivalent phantom gel to quantitatively examine the volumetric heating produced by a RF electrode catheter for transurethral prostatic thermotherapy. The specific absorption rate (SAR) of RF energy in the gel was measured from the initial transient temperatures at various locations within the gel. An expression for the SAR was proposed and its unknown parameters in this expression were determined by comparing the predicted and measured SAR values. The SAR distribution was then used in conjunction with the Pennes bioheat transfer equation to model the temperature field in prostate during the thermotherapy treatment. The prostatic tissue temperature rise and its relation to the effect of blood perfusion were analyzed. Blood perfusion is found to be an important factor for removal of heat especially at the higher RF heating level. The minimum RF power required to achieve a maximum tissue temperature above 45 °C is in the range from 14 W to 60 W depending on the local blood perfusion rate (0.2 ∼ 1.5 ml/gm/min). An empirical expression for the detailed temperature field within the prostate for various blood perfusion rates and RF power levels was also provided for clinical purposes.

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