| Purpose: 1. To investigate the thermal distribution profile and temperature curves for simultaneous application of 915MHz microwave two implanted antenna in ex Vivo bovine liver. To screen out combination of ablation parameters which can yield the most desirable coagulation geometry and volume and to compare the results with computer simulation to establish a three-dimensional thermal field for obtaining a large ablation volume at one stroke. 2. To explore the feasibility and effectiveness of this technique for treating large hepatocellular carcinoma (diameter >4cm) and cirrhosis-induced splenomegaly and hypersplenism in preliminary clinical study. Materials and Methods: 1. Ex Vivo Study: Microwave ablations were performed in fresh ex vivo bovine livers by simultaneous application of 915MHz two implanted antenna and two generator. The temperature curves at designated spots were measured in real-time by thermal couples. A total of 76 microwave ablations were performed in 18 ex vivo bovine livers and the temperature curves at 216 spot were obtained. Continuous-wave microwave ablations were induced by using four power outputs (50W, 60W, 70W, 80W) and an ablation time of 600s. Three inter-antenna distances (2.0cm, 2.5cm, 3.0cm) were used. A total of 12 experimental groups were employed in the study. 2. Establish the computer-simulated 3D thermal distribution model for simultaneous application of 915MHz microwave two implanted antenna. The 3D thermal distribution of 9 experimental groups (power outputs, 60W600s, 70W600s, 80W600s; inter-antenna distance, 2.0cm, 2.5cm, 3.0cm) were simulated by computer using finite element model. The results was compared with that of the ex vivo bovine liver ablations for calibration. The simulated temperature curves were also compared with actual temperature curves for calibration. 3. Clinical study: (1)6 HCC patientswith 6 nodules ( diameter3. 2～7. 9cm, average 4.9±1.91 cm). The maximum diameters of the tumor were measured by color doppler ultrasound. The inter-antenna distance was measured during treatment. Follow-up color Doppler ultrasound was performed 1 and 3months after treatment. Contrast-enhanced ultrasound was performed before treatment and 3days after treatment. Size of the rumor and ablation zone was measured during contrast-enhanced ultrasound. The therapeutic results were assessed by contrast-enhanced ultrasound, contrast-enhanced CT or contrast-enhanced MR. (2). 4 patients with cirrhosis-induced splenomegaly and hypersplenism. Quantitative microwave ablations were performed laparoscopically or percutaneously. Contrast-enhanced 3D CT was performed before treatment and 1 week after treatment. The volume and percentage of ablation were calculated. Peripheral blood cell count and liver function tests were recorded 7days, 14days, 1, 3 and 6 months after treatment. The intra-operative and post-operative complications were observed. Results: 1. Ex vivo study: (1) the ablation geometry for simultaneous application of two implanted 915MHz microwave two implanted antenna was related to the inter-antenna distance. The ablation zones were ellipsoidal at an inter-antenna distance of 2.0cm; A slight recess of the coagulation zone was observed in ablations at an inter-antenna distance of 2.5cm; The recess became more evident in ablations at an inter-antenna distance of 3.0cm. (2) At an inter-antenna distance of 2.0cm, after an ablation time of 600s, an ellipsoidal coagulation zone could be obtained under the four power settings (50W, 60W, 70W, 80W). No difference in geometry was observed among the four power settings. (3) The long-axis and short-axis coagulation diameter enlarge with increasing power output. However, the coagulation diameters for 70W were not different from that of 80W (P>0.05) . More desirable coagulation geometry and volume could be obtained by simultaneous application of two antenna at 70W600S with an inter-antenna distance of 2.0cm. The largest coagulation volume (7.8cmx6.1cm) was obtained by continuous-wave application at 80W600S with an inter-antenna distance of 2.0cm. 2. The computer-simulated 3D thermal distribution for simultaneous application of 915MHz two implanted microwave two antenna was obtained. The simulated thermal distribution correlated well actual temperature curves.3. Clinical study. (1)6HCC patients with 6 nodules. The patients were followed for 1-6 months. No recurrence, intra-hepatic or extra-hepatic metastases were observed. No major complications like uncontrollable hemorrhage or bile fistula occurred. (2) 4 patients with cirrhosis-induced splenomegaly and hypersplenism. Quantitative microwave ablations were performed laparoscopically(n=3) or percutaneously (n= 1). 16%-45% splenic volume was coagulated. The peripheral white blood cell count and platelet count in the 4 patients increased significantly 3 months after treatment. The serum albumin and serum total protein increased as well. Adverse effects and complications included fever, local pain, transient hemoglobinuria, mild pleural effusion and perisplenic abscess. No major complications occurred. Conclusion: 1. The ablation geometry for simultaneous application of 915MHz microwave two implanted antenna and two generator in ex vivo bovine livers is related to the inter-antenna distance. At an inter-antenna distance of 2.0cm, after 600s continuous-wave application, an ellipsoidal coagulation zone could be obtained by using the four power settings (50W, 60W, 70W, 80W). The coagulation geometry is not different among the four power settings. 2. The computer-simulated 3D thermal distribution for simultaneous appliacation of 915MHz microwave two implanted antenna and two generator using finite element model is accurate and reliable. 3. Simultaneous application of 915MHz microwave two implanted antenna two is a safe and effective method for treatment of liver cancer and cirrhosis-induced splenomegly and hypersplenism. It may be advantageous for treating large liver tumor and cirrhosis-induced splenomegaly and hypersplenism. |
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