Shear wave elastography in the evaluation of porcine liver treated with radiofrequency ablation: an in vitro experiment

Abstract

Objective To evaluate the stiffness of porcine liver in vitro treated with the radiofrequency ablation (RFA) using shear wave elastography (SWE).Methods A total number of 24pieces of porcine livers were randomly divided into 4 groups,which were treated with RFA for 6 min or 12 min,and 15 ml ethanol injection combined with RFA for 6 min or 12 min,respectively.The Young modulus were measured before ablation,after ablation immediately and 30 min after ablation when the gas disappeared in ablation zone.Results SWE imaging can clearly delineate the boundary of the stiffness changes in the RFA ablation zone,even that part was difficult to display in baseline ultrasound due to the gas hyperechogenicity reflection.The mean Young modulus before ablation、after ablation immediately and 30 min after ablation without gas reflection were (14.90 ± 4.04) kPa,(94.31 ± 23.03) kPa,(89.32 ± 20.77) kPa,respectively.Both the mean Young modulus of after ablation immediately and 30 min after ablation were significantly different from that of before ablation (P ＜ 0.001,P ＜ 0.001),but there was no significant difference between the mean Young modulus of after ablation immediately and 30 min after ablation (P =0.385).The Young modulus changes of ablation zone of RFA 6 min,12 min,15 ml ethanol injection combined with RFA 6 min or 12 min were (81.29 ± 9.19) kPa,(84.88 ± 9.89)kPa,(97.27 ±16.20)kPa,(103.82 ± 22.04)kPa,respectively.The ethanol injection combined with RFA could make the ablation zone stiffer than only RFA did (P =0.009),whereas prolonging ablation duration would make no change of stiffness in ablation zone (P =0.275).Conclusions SWE can quantitatively monitor the elasticity changes of porcine liver during RFA treatment in vitro,no matter the gas exists in the ablation zone or not.The changes of stiffness in ablation zone were different when ethanol was injected pre-ablation. Key words: Ultrasonography; Catheter ablation; Liver; Elastography