Experimental Study Of Ultrasound-guided Microwave Ablation Inducing Thyroid Cancer Apoptosis In Nude Mice

Objective:To investigate the safety and effectiveness of low-level microwave ablation therapy thyroid tumors,screened the low-level microwave ablation optimal parameters which induced thyroid cancer cells apoptosis in nude mice.Methods:Subcutaneously transplanted thyroid cancer model of 200 nude mice were established by tumor tissue block suspension,170 nude mice with similar tumor size were randomly divided into thirty-three treatment groups and one control group.The treatment groups were divided by microwave ablation time and power:165 nude mice were divided into three groups of 2min,3min,and 4min(each group with fifty-five nude mice);each time group was divided into 5W,6W,7W,8W,9W,10W,10W,11W,12W,13W,14W,and 15W groups,all those nude mice underwent ultrasound-guided microwave ablation.To compare and evaluate the effects of subcutaneous thyroid tumor ablation in nude mice,contrast-enhanced ultrasound was performed before and after ablation.After 24 hours of ablation,the pathological changes of tumor tissue were observed by HE staining,apoptosis and necrosis of tumor tissue were detected by Tunel and flow cytometry.Result:One:We successfully established subcutaneous thyroid cancer model in nude mice.Two:Ultrasound findings:the cross section of the tumor is oval,heterogeneous and low echo mass,which can detect the point-like strong echo and separation.CDFI showed a few star-shaped blood flow signals at the tumor edge and inside.Preoperative contrast-enhanced ultrasound showed that the contrast agent in the tumor was well filled.Postoperative contrast-enhanced ultrasound showed that the contrast agent in the control group was well filled,and the defect area in the treatment group was 3W in the 2min time group,8W in the 3min time group,and 8W in the 4min time group,there was no contrast agent filling in the tumor;continue increase the ablation power in each time group the tumor continuously enlarged with the increase of ablation power and time.When the microwave ablation parameters reached 1 inside is still filled with no contrast agent.Three:HE staining results:low-level microwaves could induce a large number of tumor cells to enter the apoptosis program.As power increased,the coagulation necrotic area in the tumor tissue also began to rise.Four:Tunel staining results:2min13W,3min8W,and 4min8W were the lowest microwave ablation power of each time group,increased the microwave ablation power in each time group there was no statistical difference in tumor cell apoptosis index(P>0.05).Five:Flow cytometry detect apoptosis:2min12W,3min8W,4min7W were the lowest microwave ablation power in each time group,increased the microwave ablation power,there was no statistical difference in tumor cell survival rate and apoptosis rate(P>0.05).Conclusions:Compared with the tumor cell suspension injection method,the tumor tissue block suspension injection method to establish subcutaneous thyroid cancer model in nude mice with higher success rate,shorter time,and lower cost.About 19 days after the nude mice received the tumor tissue block suspension injection the tumors were suitable in size and there was no liquefaction and necrosis,which was suitable for various experimental operations.Ultrasound guided low-level microwave ablation for subcutaneous thyroid cancer in nude mice is characterized with less trauma,well curative effect,and high safety.High power,long time microwave ablation can cause surrounding tissues damaged,the ablation power is 8W and the ablation time is 3 minutes can achieve the purpose of completely inactivating tumor tissues while reducing the related risks,which is the minimum parameter setting for microwave ablation therapy thyroid cancer in nude mice.