Feasibility study of using reduced scattering coefficient as a monitoring and evaluation factor for tumor microwave ablation therapy

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.