Background: Assessing tumor residue and local recurrent of liver malignancies after local ablation is very important for evaluating therapeutic response. This study evaluates the role of contrast enhanced ultrasound (CEUS) in assessing tumor residue and recurrent after microwave ablation (MWA) for liver malignant tumors.

Methods: 346 lesions were underwent CEUS with contrast agent Sonovue after MWA treatment. Sequoia 512 with Contrast Pulse Sequences (CPS) and Technos DU8 Contrast Tuned Imaging (CnTI)were adopted. The final diagnose were achieved by contrast-enhanced CT or contrast-enhanced MRI combined with the lever of tumour marker, histology by ultrasound guided biopsy as well as more than 6 months’ follow-up.

Results: After MWA, 27 of 346 lesions (7.80%) were showed local enhancement at tumor margin in arterial phase and diagnosed as tumor residue or local recurrent by CEUS witch were confirmed by final diagnose. Among them, 14 lesions (4.05%) were given additional MWA within 4 days after the first MWA procedure. The others were diagnosed as local recurrent one to 5 months after MWA. There were 18 lesions (5.20%) were presented untypical enhancement and diagnosis as suspected tumor residue and local recurrent. The diagnosis of false negative and the false positive was mainly occurred in lesions with hyperemic zone after MWA. Conclusions:
CEUS can accurately evaluating the tumor residue and local recurrent of liver malignancies after MWA treatment, as well as determining the necessity to continue therapy. It is a sensitive tool to assessing therapeutic response and follow-up liver malignancies after local treatment. The congestive zone after MWA is the mainly factor for diagnosis erroneously of tumor residue and local recurrent.