Needle Tract Embolization Technique In The Prevention Of Pneumothorax In Rabbit Lung Microwave Ablation

Objective:To investigate the efficacy of gelatin sponge particles and normal saline suspension in the prevention of pneumothorax after microwave ablation(MWA)of rabbit lung under the guidance of computed tomography(CT),and to observe the pathological changes.Materials and methods:24 New Zealand white rabbits were randomly divided into experimental group(n=12)and control group(n=12).Under general anesthesia,the microwave ablation antenna was punctured into the unilateral normal lung tissue by coaxial cannula technique under the guidance of CT,and the antenna was withdrawn after ablation.The coaxial cannula needle was withdrawn synchronously in the control group,and the pre-configured gelatin sponge suspension was injected through the coaxial cannula needle in the experimental group to embolize the needle tract.CT images were collected before and after microwave ablation to diagnose and evaluate pneumothorax,and the incidence and severity of pneumothorax were recorded.Two rabbits were sacrificed in each group immediately,1,3,7,10 and 14 days after ablation.The lung tissue containing needle tract were harvested,and routine HE staining was performed to observe the pathological changes of needle tract and gelatin sponge particles.Results:24 animals underwent 47 sessions of MWA(24 sessions in the experimental group and 23 sessions in the control group).There were 19 cases of pneumothorax after MWA,the incidence of pneumothorax was 40.4%(19/47),of which 3 cases(6.4%)were severe pneumothorax.The incidence of pneumothorax in the experimental group was 25.0%(6/24),and the incidence of severe pneumothorax was 4.2%(1/24),and the retraction distance on the lung surface was 0.93cm±0.87(range:0.3cm-2.5cm),while that in the control group was 56.5%(13/23)and 8.7%(2/23),and 1.15cm±0.81(range:0.3cm-3.0cm),respectively.The incidence of pneumothorax in the experimental group was significantly lower than that in the control group(P=0.028),but there was no significant difference in the severity of pneumothorax between the two groups(P>0.05).The pathological changes of the needle tract after microwave ablation are similar to those of the ablation zone,which are related to thermal injury.The needle tract was surrounded by a rim of coagulated lung parenchyma between the ablation zone and the pleura,resulting in the needle tract still open after needle withdrawal,which maybe responsible for pneumothorax after MWA.Gelatin sponge suspension can effectively seal the needle pathway,thus reducing the occurrence of pneumothorax.The tissue obtained immediately and within 3 days after MWA showed that the gelatin sponge was arranged in irregular flakes densely in the needle tract,which was effectively closed,and was absorbed and degraded 7 days later,and almost completely absorbed about 14 days later.Conclusion:Needle tract embolization with gelatin sponge after CT-guided pulmonary MWA can significantly reduce the incidence of pneumothorax.Gelatin sponge particles can effectively seal the needle pathway after ablation,and can be completely absorbed in the body with good safety.