ABSTRACT
Objective To discuss the application of MRI in making early assessment of the coagulation extent of liver tumor after microwave ablation(MWA).Methods From January 1,2015 to January 31,2016,CT-guided percutaneous MWA was employed in 46 patients with liver tumor.A total of 55 hepatic lesions were detected in the 46 patients,the mean diameter of the lesion was (26.0±5.3) mm.On the second day after MWA,MRI was performed to evaluate the ablation effect,the ablated extent (long axis×short axis) was calculated,the results were compared with the referential data provided by manufacturer.The MWA-related complications,including inadequate ablation and excessive ablation,were recorded and analyzed.Results MRI performed on the second day after MWA showed that successful MWA treatment was obtained in all the 55 hepatic lesions,and no serious complications occurred immediately after ablation.The used parameter settings of microwave energy included 60 W-5 min (n=4),60 W-8 min (n=4),60 W-10 min (n=14),70 W-8 min (n=40),70 W-10 min (n=11) and 80 W-10 min (n=18);the corresponding ablated extents produced by the above parameter settings were 41.3 mm×31.2 mm,52.0 mm×36.3 mm,51.5 mm×34.3 mm,52.9 mm×35.5 mm,56.8 mm×36.1 mm and 64.0 min×44.0 mm respectively;all the above actual ablated values were larger than the referential data provided by manufacturer,and among them the real ablated extent of 80 W-10 min group carried the biggest difference with that provided by manufacturer (64.0 mm×44.0 mm vs.54.0 mm×37.0 mm,P＜0.01).No inadequate ablation of lesion was observed,and excessive ablation was seen in 12 lesions,presenting as the involvement of the hepatic capsule or even the subcutaneous muscle layer.Conclusion Early MRI examination after MWA can precisely evaluate the ablation extent.The results of this study indicate that the actual ablated value is bigger than the referential value provided by manufacturer.Accurate prediction of ablation range before MWA is helpful in ensuring a complete ablation as well as in improving the safety of MWA.