Experimental And Primary Clinical Study Of Quantitative Splenic Microwave Ablation With Internally Water Cooled Microwave Electrode

Objective: To explore the biggest ablation volume with single internally water cooled microwave electrode, study dynamic character in the spleen and relationship with secondary Splenomegaly and hypersplenism and evaluate the efficacy and safety for quantitative microwave ablation in treatment of splenomegaly and hypersplenism.Materials and Methods: (1) Experimental Study Congestive splenomegaly were induced by ligation of the splenic vein and its collateral branches in 8 pigs. Splenic microwave ablation were performed with internally water cooled microwave electrode, 2450MHz or 915MHz frequency and serial tests with various combination of output power and duration time in 11 spots as 70W600S, 80W600S, 80W900S, 90W600S in 2450MHz frequency and 10 spots as 80W1100S, 70W1100S pulse wave, 70W600S, 80W600S continuous wave in 915MHz frequency. Eighteen spots in vitro pig livers were coagulated with combination of 915MHz frequency 80W 600S, 80W 900S, 80W 1200S, 600S+ 600S, 900S+900S and 1200S+1200S, move back the electrode 3cm in the mid of the procedure in last 3 groups. Temperature monitor was done during procedures. Length and width in vertical section of coagulation area were measured after splenectomy and volumes were calculated by software. (2) Dynamic Study Fifty six cases with cirrhosis, secondary splenomegaly and hypersplenism were divided into 3 groups of slight, moderate and severe grade of splenomegaly. Peak velocities (PV) in the blood flow spectrum of the main splenic artery, arteries in the hilum area, middle area and peripheral area weresurveyed with Doppler ultrasound and compared with the data of normal control group. Length, thickness and area of the spleen, main splenic arterial flow velocity, splenoportal venous diameter, velocity and volume of and hepatic arterial flow velocity were measured. Correlations among all these parameters above and with white blood, red blood and platelet counts were analyzed. (3) Clinical Study Microwave ablations of the spleen were performed in 25 patients with cirrhosis, secondary splenomegaly and hypersplenism, 11 were made splenectomy including 8 after the procedure and 3 just before the procedure, 14 reserved the spleen after microwave ablation whose PLT before the procedure was 53.86±20.65xl09g/L and WBC 3.03 ± 1.08xl09g/L, were separated 3 groups as laparotomy, laparoscope and ultrasound-guided. Three dimensional computed tomography (3D-CT), contrast-enhanced ultrasound (CEUS) and three-dimensional CEUS (3D-US) with magnetic tracking system were performed to calculate coagulation volume before and one week after the operation. Hepatic artery, portal vein, splenic artery and vein were also surveyed twice accordingly by CDFI. WBC, PLT, RBC counts and hepatic function were surveyed before and 3d, 7d, 14d, lm, 3m, 6m, ly, 2y after the operation. Side effects and complications during and after the procedure were observed.Results: (1 ) Experimental Study Both 2450MHz and 915MHz internally water cooled microwave electrode effectively controlled electrode temperature under 45 °C in high energy output of 70W and 80W. In vivo pig experiment, ablation volumes of 2450MHz70W600S, 80W600S and 80W900S were 27.04±1.86ml~ 42.65±2.45ml, 915MHz pulse wave of 70W1100S and 80W llOOS were 41.40+ 7.21ml~64.68 + 5.12ml and 915MHz continuous wave of 70W 600S and 80W 600S were 48.39 + 52.99ml ~ 70.78 ± 2.30ml. Compared separately the three items of different combination of frequency, output power and ablation time, an optimal coagulation volume of 915MHz continuous wave 80W600S was got of 70.78+2.30ml. Moreover, in vitro experiment, when the procedure time was prolonged to 900S, 1200S, bigger coagulation volumes were got. 90.05±7.83mlwas obtained with the combination of 915MHz 80W900S. Prolonged the time to 900S+900S and 1200S+1200S, move back the electrode 3cm in the mid of the procedure, coagulation volumes continually were improved for single electrode pass. (2) Dynamic Study Compared with the data of control group, PV of the main splenic artery, arteries in the hilum area, middle area ascend significantly along with the spleen size in 3 splenomegaly groups (P<0.05), while arterial PV in peripheral area showed no significant difference (P<0.05). Velocity in the inferior part of the spleen obviously lower than the superior and middle part (P=0.0004). Analysis of the relationship among portal hypertension, splenomegaly and Hypersplenism, splenic length and area were negatively correlated with splenoportal diameter and flow volume. White blood count also was negatively correlated with splenic length, area, splenoportal diameter and flow volume. Though there were no correlation between RBC, PLT count and splenic size, PLT count was negatively correlated with splenic artery velocity (r=-0.3817), splenic vein diameter (r=-0.4017) or blood flow volume (r=-0.3813). (3) Clinical Study There was no spot bleeding after the procedure in patients performed microwave ablation before splenectomy. Affected by high velocity of human blood flow, coagulation volume of the spleen with 915MHz 80W600S was only 23.28 + 5.07ml, which is much lower than vivo results. In 14 patients reserved the spleen after microwave ablation, mean ablation volume was 142.85 + 67.01ml (56.76~286.75ml) and ablation proportion was 22.44% ±9.95% (7.40%~40.26%). There was no significant different between volumes calculated by 3D-CT and 3D-CEUS with magnetic tracking system for small coagulation area. With the ablation of average splenic coagulated volume of 20%, WBC and PLT counts ascended obviously. PLT count reached peak 14 days after the procedure and then descend slightly but still higher 6 months ~2 years later than the level before ablation. The ascending degree of PLT in 14 days had linear correlation with ablation proportion (r=0.8006, p=0.0054). Liver function and hepatic artery blood flow improved significantly comparing with data before the procedure. Sideeffects and complications were fever, abdominal pain, temporal haemoglobinuria, temporal amylopsin ascent and smear to middle pleural effusion. Conclutions: Internally water cooled microwave electrode of 915MHz can get big ablation volume with combination of continuous wave, high output power, longer ablation time and move back the electrode regularly during operation. Quantitative microwave ablation of the spleen with 915MHz internally water cooled microwave electrode is safe and feasible. Ablated proportion of 20%~40% each time can improve blood cell count effectively without severe complication risk.