QUANTIFICATION OF THE 3-D ELECTROMAGNETIC POWER ABSORPTION RATE IN TISSUE DURING TRANSURETHRAL PROSTATIC MICROWAVE THERMOTHERAPY USING HEAT-TRANSFER MODEL

Experiments were performed in a tissue microwave-equivalent phantom ge l to quantitatively examine the volumetric heating produced by a micro wave antenna with a peripheral cooling system for the transurethral pr ostatic thermotherapy, Based on previous research, expression for the specific absorption rate (SAR) of microwave energy in the gel was exte nded to three dimensions, which includes its dependence on radial, ang ular, and axial direction. A theoretical heat transfer model was devel oped to study the temperature distribution in the gel by introducing t his proposed SAR expression. The parameters in this expression and the convection coefficient due to the chilled water running around the an tenna were determined using a least-square residual fit of the theoret ical temperature predictions to the experimentally measured steady-sta te temperature field within the gel. The analytical expression of the three-dimensional SAR distribution obtained in this study will help pr ovide a better understanding of the microwave heating pattern in the p rostatic tissue and, thus, to aid in designing improved applicators. I t can also be used in the future as an accurate input to heat transfer models which predict temperature distributions during the transurethr al microwave thermotherapy.