Microwave Ablation: An Experimental Comparative Study on Internally Cooled Antenna versus Non-internally Cooled Antenna in Liver Models

Rational and Objectives: Microwave ablation is an alternative therapy with high cost-effectiveness for liver malignancy. The authors designed this experiment to compare the effect of microwave ablation using a non-internally cooled (NIC) antenna with that using an internally cooled (IC) antenna in both an ex vivo and an in vivo liver models. Materials and Methods: Sixty-two microwave ablations were performed in ex vivo porcine and in vivo canine liver models (NIC antenna, 28 coagulations; IC antenna, 34 coagulations). Pair comparisons were executed in terms of the coagulation parameters, including short-axis diameter (SD), long-axis diameter (LD), and spherical ratio (SR, SD/LD). The distributions of tissue temperatures were compared in ex vivo ablation. During in vivo ablation, the temperatures of antenna shaft were measured and unintended tissue coagulation were observed and compared. Results: In both ex vivo and in vivo ablations, less charring areas were found around the IC antenna shaft. With a longer SD (P<.01) and a shorter LD (P<.01), the coagulations of IC antenna appeared to be more spherical than those of NIC antenna (P<.01). During ablations in vivo, the temperatures of NIC antennas shaft were up to 90 degrees C or even higher, which resulted in some unintended tissue coagulation, whereas the temperatures of IC antennas shaft were lower than 20 degrees C in all ablation processes without any unintended tissue coagulation (P<.01). Conclusion: The IC antenna performed better than NIC antenna in microwave ablation for liver models and might be more suitable for therapy for liver malignancy in clinical practice.