Study Of Influencing Factors In Water Cooled Microwave Ablation In Hepatic Tissue And Risk Factors Of Hepatocellular Carcinoma Recurrence After Microwave Ablation

Objective Study the influence of microwave power and ablation time to the magnitude of clotting region in internally water cooled microwave hepatic tissue ablation, study the difference between 915MHz and 2450MHz microwave in ablation zone and temperature curve and analyze the risk factors of recurrence in the patients of hepatocellular carcinoma who treated by internally water cooled microwave ablation.Materials (1) ex vivo experiment: We did 180～220 microwave ablation experiments and measured 80～100 points' temperature in 90 ex vivo ox hepatic tissue. According to the power they were divided into three groups: group A(60W600s), group B(60W1200s) and group C(80W600s), according to the frequency of microwave they were divided into group of 915MHz and group of 2450 MHz. (2) in vivo experiment: we did 40～45 ablation experiments in 8 little swine, among which there were four groups: group A(50W600s), group B(60W600s) ,group C(70W600s) and group D(80W600s),and according to the frequency of microwave they were divided into group of 915MHz and group of 2450 MHz as above. (3) Clinical analyze: there are 350 patients who treated by internally water cooled microwave ablation from October of 2005 to February of 2007 in our hospital. We enrolled hepatocellular carcinoma patients who treated by single irradiation and by one time microwave ablation, studying the influence of different time to clotting region in 50W, of which there were 4 groups, group A:180s, group B:300s, group C:600s and group D:900s.In the second part, we followed up the 78 hepatocellular carcinoma patients 1month later who treated by nothing-else therapy but MW and are ablated completely, and we divided them into recurrent group and recurrence-free group by enhancing CT or MRI and CEUS. Multivariate Logistic regression was used to identify independent relative factors of recurrence among those that was significantly difference between above two groups.Result (1)ex vivo experiment: If giving larger power or longer ablation time in 2450MHz, we would increase the volume of ablation zone (60W600s 23.9cm~3 vs. 60W1200s 72.2 cm~3 and 60W600s 23.9 cm~3 vs. 80W600s 30.8 cm~3,P<0.05); of which until 1500s, longer time played more important role than larger power ( ⊿1200s-600s 48.3 cm~3 vs.⊿80W-60W 6.9 cm~3,P<0.05) ; when ablation time was 600s, 915MHz would bring bigger ablation zone than 2450MHz in all levels of power(50W: 34.6 cm~3 vs. 19.8 cm~3 , 60W43.4 cm~3 vs. 23.9 cm~3, 70W64.7 cm~3 vs. 28.7 cm~3 , 80W88.7 cm~3 vs. 30.8 cm~3, P<0.05). (2) in vivo experiment: When ablation time was 600s and frequency was 915MHz, increasing the power would enlarge the ablation zone (50W18.2 cm~3 vs. 60W24.2 cm~3 vs. 70W25.3 cm~3及 80W37.1 cm~3, P<0.05); as ex vivo experiment, when ablation time was 600s, 915MHz would bring bigger clotting region than 2450MHz in all levels of power (50W: 20.7 cm~3 vs. 18.2 cm~3 , 60W30.7 cm~3 vs. 24.2 cm~3, 70W28.0 cm~3 vs. 25.3 cm~3 , 80W40.8 cm~3 vs. 37.1 cm~3 , P <0.05). (3)clinical analyze: When power was 50W and frequency was 2450MHz, increasing the ablation time would enlarge the ablation zone (180s1.53 × 1.70cm vs. 300s1.64X 2.01cm vs. 600s2.26×4.23cm vs. 900s2.50×4.40cm, P<0.05).Among the second part patients, there were 20 who had recurred. Single-variable analysis showed that number of the tumor, pathology grade, location near to big tubing, and ablation margin of safety were difference significantly between the recurrent group and non-recurrent group, Multivariate Logistic regression analysis demonstrated that number of the tumor was the risk factors of recurrence.Conclusion Through increasing power and ablation time and reducingfrequency we could enlarge the clotting region, of which longer time played more important role than larger power; Number of the tumor was the risk factors of recurrence.