Aiming at the problem that in microwave tumor ablation surgery, there is a lack of 2D curative effect evaluation method during and after clinical operations. This article discusses whether the infrared thermal imaging method can be used as an effective 2D evaluation method. This paper conducted two sets of experiments to validate whether the infrared thermal imaging method is effective and whether it can be used in real-time monitoring. In the experiments, microwave ablation system is used to conduct in vitro porcine liver ablation with different times and powers. In the first set, the size and shape of the ablation area are measured after the ablation time is completed, then actual ablation results, infrared thermal imaging results and simulation results are compared. In the second set, the infrared thermal imaging results are captured every minute during the ablation process, then compared with simulation results at each minute. Results show that the size and shape of the ablation area from the actual ablation experiments, the infrared thermal imaging method and the simulation are consistent, also the temperature change and the distinction of the different ablation zones are also consistent. In addition, second set experiment results are consistent with the intraoperative results. These results validate that the infrared thermal imaging method can be used as an effective real-time intraoperative and postoperative curative 2D evaluation method.
Finding an effective monitoring and evaluation factor for therapeutic effect of microwave ablation is becoming a research focus. Previous MWA experiments on in vitro porcine liver found that reduced scattering coefficient ( μ's ) is an efficient optical evaluation parameter. Results indicated that μ's of normal tissue and coagulation tissue is 3-5 cm-1 and 17-19 cm-1, respectively, and μ's is highly related to the degree of thermal damage. This paper aims to validate if these results from in vitro porcine liver also applies to real tumor. Two sets of experiments were carried out with human liver tumor specimens. In the first experimental set, the tumor specimen was heated by water bath at constant temperature of 80 ℃ for 5 minutes, and μ's was obtained before and after the heating process. In the second set, another tumor specimen was heated by MWA with microwave power of 10 W for 5 min, reduced scattering coefficient and temperature changes were measured during ablation. In the first experiment, μ's value was 4.10 cm-1 before heating and increased to 17.16 cm- 1 after complete tissue protein coagulation. In the second experiment, μ's grew exponentially first and eventually stabilized. μ's values are consistent with previous experiments on in vitro porcine liver. These results also validates that the μ's values reflect the degree of thermal damage, and be captured in real-time. To sum up, μ's is an effective real-time thermal damage monitoring and evaluation factor that can be applied to real tumors.
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