Abstract: Background and purpose: Thermal ablation (radiofrequency ablation, RFA/microwave ablation, MWA) is the most commonly used minimally invasive technique for the treatment of liver cancer. Real-time shear wave elastography (SWE) is a new type of ultrasonic imaging technology, which was used in our study to monitor thermal ablation of liver cancer. This study aimed to investigate the stiffness change of liver cancer and that of surrounding liver parenchyma before and after thermal ablation, and to evaluate the application of SWE for monitoring thermal ablation for liver cancer. Methods: From Oct. 2014 to Apr. 2015, a total number of 36 patients, with 39 lesions, were treated with RFA or MWA and got complete response. SWE examination was performed before and after ablation. The SWEmean, SWE-min, SWE-max, SWE-SD of lesions and the surrounding liver parenchyma were measured. Statistical analysis was made to compare the stiffness changes of liver cancer with those of the surrounding liver parenchyma before and after thermal ablation, and to determine whether there were differences between two different ablation modes. Results: Before and after ablation, the SWE-mean of lesions was (30.09±11.67) kPa vs (52.11±17.56) kPa, SWE-min was (10.46±8.22) kPa vs (20.57±11.42) kPa, SWE-max was (51.50±20.84) kPa vs (88.54±27.75) kPa, SWESD was (10.63±4.30) kPa vs (16.89±7.72) kPa; There were statistically significant differences (P<0.05). Before and after ablation, the SWE-mean of surrounding liver parenchyma was (8.84±2.82) kPa vs (8.91±2.78) kPa, SWE-min was (4.77±1.95) kPa vs (4.69±1.90) kPa, SWE-max was (13.82±3.79) kPa vs (14.34±3.97) kPa, SWE-SD was (3.24±1.32) kPa vs (3.37±1.29) kPa; There were no statistically significant differences (P>0.05). After ablation, the SWE-mean of RFA and MWA was (45.55±10.91) kPa vs (60.59±20.99) kPa, SWE-min was (18.95±8.86) kPa vs (25.93±10.93) kPa, SWE-max was (76.58±15.51) kPa vs (104.01±32.59) kPa, SWE-SD was (13.82±3.52) kPa vs (20.85±9.77) kPa; There were statistically significant differences (P<0.05). Conclusion: SWE can quantitively analyze the stiffness of lesions. The ablation zone became stiffer after RFA or MWA, and the ablation zone of MWA was stiffer than that of RFA. Two kinds of ablation methods did not significantly affect the stiffness of liver parenchyma around the lesion. SWE could potentially be used to monitor thermal ablation of liver cancer.

Key words: Real-time shear wave elastography, Liver cancer, Radiofrequency ablation, Microwave ablation