The Experimental Study Of Radiofrequency Ablation And Microwave Ablation In Vitro Bovine Liver

Objective:Although the mechanism is different, radiofrequency ablation and microwave ablation all belong to the thermal ablation mode. Each of the application of both has a large number of reports. The ablation effects are affirmed both of them in malignancy. Currently, two methods are considered as good efficacy of small hepatocellular carcinoma as surgery. However, comparative studies reported in the literature were less and different in conclusions between them. This study is to compare of the effect of the two ablation ways and observe each ablation characteristics in vitro bovine liver.Methods:Experiment was divided into two groups:Group RF and Group MW. Two groups respectively used Cool-tip RF eletrode and Water-cooled Microwave antenna. According to different ablation time, each group was divided into four subgroups: Subgroup4min, Subgroup6min, Subgroup8min and Subgroup10min. The experiment of each subgroup was repeated three times by single-needle and single-ablation method. At the end of the ablation, instantly measured the longitudinal diameter of ultrasound hyperechoic area. Observed the ablation lesion and measured longitudinal diameter and transverse diameter after cutting the bovine liver along the eletrode or antenna. Calculated the volume of the ablation lesion after the experiment.Results:The hyperechoic area appeared rapidly around the ablation needle and expanded outwards gradually at the beginning of the experiment. The hyperechoic area was not significantly increased after six minutes. Longitudinal diameter of ultrasound hyperechoic area was between6.0cm-6.4cm in Group RF and between6.2cm-6.6cm in Group MW from six minutes to ten minutes. The cut surface of ablation lesions were oval, yellowish-white. Naked eye could clearly distinguish between the ablation lesion and surrounding tissue. Compared with group RF, tissue carbonization was more apparent around the needle tract in group MW. The size of carbonization zone was (2.8-3.1)cm×(0.5-0.7)cm. Ablation lesion’s longitudinal diameter and transverse diameter of both Groups increased slowly in about6minutes.Compared with the actual measurements, the size of longitudinal diameter of ultrasound hyperechoic areas were larger(P<0.05). And there was a high degree of linear correlation between them(rR=0.779, rM=0.882, P<0.05). Volume of the ablation lesions had significant differences between adjacent subgroups in Group RF(P<0.05). Volume of the ablation lesions had significant differences between Subgroup4min and Subgroup6min, Subgroup6min and Subgroup8min in Group MW(P<0.05). Subgroup10min’s ablation lesion’s volume was greater than Subgroup8min’s, but there was no statistically significant differences between them in Group MW (P>0.05). Microwave ablation lesions longitudinal diameter and volume were greater than the corresponding time radiofrequency ablation lesions longitudinal diameter and volume in4minutes,6minutes and8minutes (P＜0.05). Longitudinal diameter and volume of microwave ablation lesions has no statistically significant difference with longitudinal diameter and volume of radiofrequency ablation lesions in10minutes (P>0.05). Microwave ablation lesions transverse diameter was greater than that of radiofrequency ablation lesions in4minutes (P=0.034＜0.05). Transverse diameter of microwave ablation lesions has no statistically significant difference with that of radiofrequency ablation lesions in6minutes,8minutes and10minutes (P>0.05).Conclusions:Both Radiofrequecy and Microwave in the ablation of vitro bovine liver can obtain a stable spheroidal ablation lesions by single-needle and single-ablation method. Compared with radiofrequency ablation, microwave ablation has a higher thermal efficiency and a faster ablation speed. But with time, both of them can achieve a similar effect of ablation eventually. It is easy to puncture accurately and monitor the ablation process real-time under ultrasound. But the range of ablation lesions can not be clearly observed. There is certain correlation between the hyperechoic area size and the actual size of the ablation lesions.