| Background:Surgical resection is still the most important method for the treatment of liver occupancy lesions.With the gradual understanding of the liver anatomy,the improvement of anesthesia and postoperative monitoring,the improvement of surgical technique and the invention and application of advanced surgical instruments,the safety of hepatectomy has been greatly improved,the therapeutic effect has been improved obviously,and the incidence of surgical complications and surgical-related mortality have significantly reduced.Hepatic surgery has been developed from the blind hepatectomy to the precise hepatectomy combined with digital medicine,and the complete theoretical system and operational norms have been established in nowadays.Minimally invasive surgery is the concept and development direction of traditional surgery.Laparoscopic hepatectomy has been widely used in the field of hepatic surgery since it was first reported in 1991 by Reich,a professor of ostetrics and gynecology in the United States,with its minimal injuary,rapid postoperative recovery,slight systemic reactions and other virtues.Due to the particularity of laparoscopic surgery itself,it is difficult to stanch bleeding through means of bundling,pressing or packing which were commonly used in traditional open surgery.The results are often tend to be fatal if the bleeding is difficult to control in the process of liver parenchyma dissection.Therefore,the exploration of new techniques for safe laparoscopic hepatectomy and the development of highly efficient surgical related devices are the fundamental way to promote the development of minimally invasive liver surgery.Objective:In this study,we explored the laws of the distribution of 60 oC thermal fields of 915 MHz microwave antenna under different emission powers and emission durations by computer simulation and multi-points temperature-measuring in phantom,to preliminarily estimate the feasibility of 915 microwave antenna used for laparoscopic hepatic parenchymal dissection.To verify the accuracy of the computer simulated temperature fields,we performed thermal coagulation experiments in excised porcine livers,discarded human livers and intravital porcine liver,and we screened out the optimal parameter,which can be used for laparoscopic hepatectomy.At last,we evaluated whether the use of 915 MHz microwave pre-coagulation assisted liver resection could reduce intraoperative blood loss,shorten the time of liver parenchymal dissection and reduce damage to postoperative liver function,and determine whether it could reduce the incidence of postoperative complications by analyzing the clinical data of 60 patients who underwent laparoscopic hepatectomy from January 2001 to June 2016 in our center.Methods:1.We simulated the 60 ℃ thermal fields of the 915 MHz microwave antenna under different combinational parameters of the emission powers of 30W,40W,50W,60W,70W,80W and the emission durations of 50s,100s,150s,and 200s in phantom by using the finite element method.2.We performed the thermal coagulation experiments with the emission power of 30W,40W,50W,60W,70W,80W and emission durations of 50s,100s,150s and 200s in the excised porcine livers.Observe the geometrical shape of coagulated regions in the liver parenchyma formed by 915 MHz microwave antenna and measure the length and width of the coagulated area,preliminarily screened out the appropriate parameter combination which meet the requirement of hepatic parenchyma dissection.3.We performed coagulation experiments in discarded human livers with the parameters based on the results on simulated thermal fields and discarded porcine livers to observe the geometrical shape and measure the length and width of coagulated regions to compare the differences in coagulation effect of discarded human livers and isolated porcine livers under the same emission parameter and assessed the loss of residual liver parenchyma.4.We performed the coagulation experiments in intravital porcine livers with selected parameters combination to determine the antenna interval used for microwave assisted laparoscopic hepatectomy.5.We analyzed the clinical data of 60 patients who underwent laparoscopic hepatectomy from January to June 2016 in our center.In addition,we compared the differences of duration of dissection of liver parenchyma,the duration of operation,the amount of blood loss and compared the serum concentration of alanine aminotransferase(ALT)and aspartate aminotransferase(AST)in the first,the third,and the fifth day after operation in two groups.We reviewed and analyzed the postoperative bleeding,bile leakage,abdominal infection,liver failure and other complications and perioperative mortality in two groups.Results:1.Computer simulated 60 ℃ two-dimensional temperature fields of the internal circulation of water-cooled 915 MHz microwave antenna were axisymmetric distributed oval with the antenna as the axis.The geometric size of the thermal fields at 60 ℃ were increased with the increase of the emission time and the emission power.The length of 60 ℃ thermal fields ranged from3cm to 7cm and the width ranged from 1.3cm to3.3cm.The main factors affecting the length was the microwave emission power and the main factor affecting the width was the microwave emission time.2.The geometrical shape and range of the coagulated region in excised porcine livers were consistent with the simulated temperature fields of 60 ℃.The length and width were 5 cm,1.5cm respectively with the emission parameters of 50 W/100 s.3.Cylindrical coagulated regions could be formed in discarded human livers by 915 MHz microwave at 50W/100s.4.Coagulation experiment in intravital porcine livers revealed the geometrical shape and range of the coagulated regions are the same as those of the excised porcine livers at 50 W/100 s.A completely coagulated zone could be obtained in intravital porcine liver at an antenna interval of 2cm.5.There were no significant differences in age,sex,tumor size and location,preoperative liver function and other clinical data(P>0.05)between two groups.All of the operation were successfully completed,there was no perioperative death occurred.The operation time(120.67 ± 27.16min vs 148.00 ± 29.61min,P<0.001),the time of hepatic parenchymal transaction(55.17 ± 14.17min vs 70.83 ± 14.44min,p<0.001)and the hepatic portal occlusion time(2.17 ± 4.09 min vs 25.33 ± 20.63 min,p<0.001)in microwave group were less than control group.The intraoperative blood loss in the microwave group was significantly lower than that in the control group(26.83 ± 18.82 ml vs 186.33 ± 86.16 ml,p<0.001),the difference was statistically significant.There was no significant difference in concentration of preoperative serum ALT and AST between the two groups(p=0.746,,p=0.529),but the liver function damage were observed in both group after surgery.The levels of serum ALT and AST in the microwave group were significantly lower than those in the control group(p<0.05)in the first and third day after surgery.On the fifth day after operation,the serum level of ALT in the microwave group was lower than that in the control group,but there was no difference between the two groups in AST level.In the control group,there were 2 cases of bile leakage,1 case of abdominal infection and 1 case of abdominal hemorrhage,all of these patients were cured after appropriate treatment,there was no complication in the microwave group,the difference was statistically significant(p=0.038).The mean intraperitoneal drainage of microwave group in the 1st,3rd,5th day after operation were less than that of the control group(p<0.05),and the average postoperative hospital stay in the microwave group was less than that in the control group(6 ± 1.31d vs 7.23 ±2.66d,p=0.027).Conclusion:1.The geometrical shapes and range of the coagulated zone in the liver parenchyma can be accurately predicted by 60 oC thermal fields simulated by computer through multi-points temperature-measuring in phantom.2.915 MHz microwaves can be used to coagulate the liver parenchyma on transection plane at low power/short-term emission parameters.3.50W/100s are the optimal parameters for thermal coagulation of liver parenchyma.4.Under the condition of microwave emission duration of 100s,the blood flow of living liver had no significant effect on the geometry shape and range of the coagulated region.5.Laparoscopic hepatectomy could be performed efficiently and safely with minimal injury of liver parenchyma and ’blood loss when assisted with 915 MHz microwave coagulation.Compared with traditional laparoscopic liver resection technique,it can significantly reduce bleed loss,shorten the operation and anesthesia duration,have less damage on postoperative liver function and effectively reduce the risk of postoperative complications,especially for patients with cirrhosis. |
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