Numerical study on thermal field of microwave ablation with water-cooled antenna.

ABSTRACT

PURPOSE: This research was to reveal the thermal characteristics of a water-cooled microwave ablation antenna in phantom, and the influence of cooling water velocity on ablation pattern by numerical method. In addition, by comparing the numerical results with experimental results, the experimentally obtained SAR was proven to be correct. METHODS: The temperature distribution in ablations was simulated by the finite element method. In the FEM, the cooling effect in the region of the water-cooled antenna was introduced by applying the convective coefficient to the related boundaries, and the experimental determined SAR in phantom was applied as heat generation of microwave generator. To study the effect of water flow rate on ablation pattern, three different water velocities were chosen. In addition, the phantom thermal properties changes were considered in simulation when the heating temperature was above 80 degrees C. RESULTS: The ablation pattern could be identified as a pear shape. The temperatures of monitoring points which were located near the antenna could rise more rapidly, and they were more likely to achieve steady heat transfer state within a short time compared with those far away from the antenna. The cooling water effectively decreased the temperature near the antenna, an under-temperature occurred in the cooling region, and the different cooling water flow rate did not affect significantly the ablation pattern. CONCLUSIONS: The numerical results compared reasonably well with the experimental results in both heating pattern and temperature of individual monitoring point over the same heating duration. The SAR measured by our previous experiment was also confirmed by this numerical simulation. This method could be employed to study combination thermal field of multi-antennas in future work.